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Ozone layer depletion - class-XI

Description: ozone layer depletion
Number of Questions: 109
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Tags: global environmental change commercial applications zoology depletion of resources biology environmental issues ecology and environment
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Ozonosphere occurs at height of

  1. 8-10 km. above poles

  2. 8-10 km. above equator

  3. 11-16 km above poles

  4. 11=-16 km above equator


Correct Option: C

Which of the following statement/s is/are correct with regard to ozone depletion:
1. The ozone hole is measured in terms of ozone concentrations, which is expressed in Dobson units.
2. The major cause for ozone depletion is the presence of CFCs in the stratosphere - CFCs are entirely man-made and not found naturally.

  1. Only 1

  2. Only 2

  3. Both A and B

  4. None of the above


Correct Option: C
Explanation:

  • CFCs and other halogenated ozone depleting substances (ODS) are mainly responsible for manmade chemical ozone depletion.
  • The total amount of effective halogen (Chlorine and bromine) in the stratosphere can be calculated and are known as the equivalent effective stratospheric chlorine.
So, the correct option is 'Both A and B'.

Snow blindness is cause due to

  1. Ozone hole

  2. Nuclear winter

  3. Acid rain

  4. Green house effect


Correct Option: A
Explanation:

Cataracts and blindness are among the most common eye diseases associated with further ozone layer depletion and increased UV-B at the Earth's surface.  A 1% decrease in stratospheric ozone may result in 100,000 to 150,000 additional cases of blindness due to eye cataracts worldwide. The ozone layer is responsible for absorbing harmful ultraviolet rays, and preventing them from entering the Earth's atmosphere.

So the correct answer is 'Ozone hole'.

Identify the wrong statement with reference to UV rays.

  1. UV-A is more harmful to animals than UV-B.

  2. UV radiation falls in the range between 100-300 nm wavelength.

  3. UV radiation is classified into three categories.

  4. UV radiation kills microorganisms.


Correct Option: A
Explanation:

  •  The UV region covers the wavelength range 100-400 nm and is divided into three bands: UVA (315-400 nm) UVB (280-315 nm)
  • The most common form of UV radiation is sunlight, which produces three main types of UV rays: UVA, UVB, UVC.
  • At certain wavelengths, UV is mutagenic to bacteria, viruses and other microorganisms. Particularly at wavelengths around 260–270 nm, UV breaks molecular bonds within microorganismal DNA, producing thymine dimers that can kill or disable the organisms.
  • UVB, the chief cause of skin reddening and sunburn, tends to damage the skin's more superficial epidermal layers. It plays a key role in the development of skin cancer and a contributory role in tanning and photoaging.

So, the correct answer is 'UV-A is more harmful to animals than UV-B.'.

Exposure of UV radiations causes

  1. Damage to eye sight

  2. Sunburn

  3. Skin cancer

  4. All of the above


Correct Option: D
Explanation:

The exposure to the UV radiations have an ionizing and distorting effect to the body of the humans. It causes damage to the eyes by destroying the essentials of the eye-lens. The sunburn occurs due to high intensity. Skin cancer is caused due to distortion of the DNA by the formation of the pyrimidine dimers, such that the DNA cannot be replicated properly.

Hence, the correct answer is 'All of the above'.

An ozone depleting chemical, which is used in fire- extinguishers is ________.

  1. Nitrogen oxide

  2. Methyl bromide

  3. Halon

  4. Chlorofluorocarbon


Correct Option: C
Explanation:

Methyl bromide, halon, nitrogen oxides and chlorofluorocarbons are the potent ozone-depleting substances. These accumulate in the stratosphere and undergo photodissociation when exposed to the UV rays. The reactive chlorine and bromine react with ozone to form diatomic oxygen and molecular oxygen.

A. Nitrogen oxides are released from the vehicular exhausts and industrial emissions.
B. Methyl bromide was used as a fumigant.
C. Halon was used as fire-extinguisher.
D. Chlorofluorocarbons were used as refrigerants.
Hence, the correct answer is 'Halon'.

Role of CFC present in atmosphere is

  1. Reduction in ozone

  2. Ozone formation

  3. Formation of leghaemoglobin

  4. Enhance chlorophyll formation


Correct Option: A
Explanation:

The ozone layer is part of the earth's atmosphere. Ozone is basically found in the stratosphere. Ozone layer contains the high concentration of ozone. It's is vital to human life on earth because it absorbs biologically harmful ultraviolet radiations from the sun. Direct exposure to such rays can cause serious illness and skin problems. The main cause of ozone depletion is manufactured chemicals especially CFCs, these compounds reach the stratosphere by winds, where they release halogen atoms through photodissociation and cause the breakdown of ozone into oxygen. The ozone hole formed due to this increase the exposure of direct UV rays on earth carrying the potential risk of skin cancer and other negative effects.

Hence, the correct answer is 'Reduction in ozone'

Melanin protects us from

  1. X-rays

  2. Infra-red rays

  3. Visible rays

  4. UV rays


Correct Option: D
Explanation:

The intermediary lobe of the pituitary gland secreted the Melanocyte Stimulating Hormone (MSH) that acts on the types of cells in the skin called the melanocytes. These cells produce a coloured pigment called the melanin which diverts the UV-A radiations falling on the skin. This prevents the UV rays from reaching to the other sensitive cells of the body and prevents the possible damages to the DNA that can be caused by them. This is the reason that body develops tanning when exposed to the bright sunlight. It is a protective mechanism.

Hence, the correct answer is 'UV rays'.

Chlorofluorocarbons are not being used in refrigerators because they

  1. Increase temperature

  2. Cause allergic reactions

  3. Deplete ozone

  4. Both A and B


Correct Option: C
Explanation:

Among the five layers of the earth's surface ozone is present in the stratosphere which absorbs UV radiation before it reaches the ground. The main cause of ozone depletion is manufactured paraffinated halogen chemicals especially CFCs, these compounds reach the stratosphere by winds, where they release halogen atoms through photodissociation and cause the breakdown of ozone into oxygen. The ozone hole formed due to this increase the exposure of direct UV rays on earth carrying the potential risk of skin cancer and other negative effects.

Hence, the correct answer is 'Deplete ozone'.

Ozone hole causes

  1. Global warming

  2. Reduction in the rate of photosynthesis

  3. More ultraviolet rays come to earth

  4. All of the above


Correct Option: C
Explanation:

Among the five layers of the earth's surface ozone is present in the stratosphere which absorbs UV radiation before it reaches the ground. The main cause of ozone depletion is manufactured chemicals especially CFCs, these compounds reach the stratosphere by winds, where they release halogen atoms through photodissociation and cause the breakdown of ozone into oxygen. The ozone hole formed due to this increase the exposure of direct UV rays on earth carrying the potential risk of skin cancer and other negative effects. Direct exposure of harmful UV rays that penetrates skin can damage the genetic material I.e., DNA in skin cells and if the body is unable to recover the damage the cells stars to divide and grow uncontrollably which eventually leads to a tumour.

Hence, the correct answer is 'More ultraviolet rays come to earth'

Result of ozone hole is

  1. Green house effect

  2. Global warming

  3. Acid rain

  4. UV radiations reach the earth


Correct Option: D
Explanation:

Ozone is found in high concentration in the stratosphere of the earth's surface in the form of ozone blanket or commonly known as the ozone layer. The vital function of ozone is to absorb the sun's ultraviolet radiation before it reaches the ground hence protecting the earth from its harmful effect. But the ozone-depleting substance such as Chlorofluorocarbons, nitrous oxides, etc that reacting with the ozone layer cause depletion of it forming ozone hole.

Hence, the correct answer is 'UV radiations reach the earth'.

Depletion of ozone layer is due to _______.

  1. Oxides of nitrogen

  2. Oxides of carbon

  3. Oxides of sulphur

  4. None of the above


Correct Option: A
Explanation:

Oxides of nitrogen find their way to the environment when they are released from the fertilizers, farms, combustion of coal etc. These bear a similarity to the paraffinated halogens like the chlorofluorocarbons when they reach the stratosphere of the atmosphere. They get unstable when exposed to the UV rays and the reactive nitrogen atom recs with the ozone to form the nitrogen dioxide and the diatomic oxygen molecule, similar to the reaction catalysed by the CFCs which release reactive chlorine that break down the ozone.

Hence, the correct answer is 'Oxides of nitrogen'.

Natural sink of stratospheric ozone is?

  1. Sulphuric dioxide

  2. Sulphur fluxes of oceans

  3. Freons

  4. HCFCs


Correct Option: D
Explanation:

The main cause of ozone depletion and the ozone hole is manufactured chemicals, especially manufactured halocarbon refrigerants, solvents, propellants and foam-blowing agents (chlorofluorocarbons (CFCs), HCFCs, halons), referred to as ozone-depleting substances (ODS). These compounds are transported into the stratosphere by the winds after being emitted from the surface.[2] Once in the stratosphere, they release halogen atoms through photodissociation, which catalyze the breakdown of ozone (O3) into oxygen (O2).[3] Both types of ozone depletion were observed to increase as emissions of halocarbons increased.

So the correct answer is 'HCFCs'.

Chlorofluorocarbon releases ______ which is harmful to ozone.

  1. Fluorine

  2. Chlorine

  3. Nitrogen peroxide

  4. Sulphur dioxide


Correct Option: B
Explanation:

Chlorofluorocarbons are the halogenated paraffin hydrocarbons containing chlorine, fluorine and carbon. These have been extensively used as the refrigerants and the spray propellants due to their non-toxic nature. But, the CFCs have found their way to the stratosphere of the atmosphere where the incidence of the UV rays is very high. The CFC splits up when exposed to the UV rays and release the reactive chlorine species. This is harmful to the ozone in the stratosphere because the chlorine reacts with ozone to release the simple oxygen, that is further converted to the reactive nascent oxygen.

Hence, the correct answer is 'Chlorine'.

In coming years, skin related disorders will become more common due to ________.

  1. Excessive use of detergents

  2. Water pollution

  3. Air pollution

  4. Depletion of ozone layer


Correct Option: D
Explanation:

The ever increase in the use of ozone-depleting substances like CFCs, HFCs, methyl bromide etc. will continue destroying the ozone layer in the stratosphere. The depletion of the ozone layer will result in the penetration of more UV-A and UV-B radiations to the earth surface. These radiations are strong mutagens as they distort the structure of the skin cell DNA when the skin is exposed to the UV rays. It results in skin related disorders like pigmentation, skin cancer etc. 

Hence, the correct answer is 'Depeletion of the ozone layer'.

Ultraviolet radiations from sunlight cause a reaction which produces

  1. $O _3$

  2. $SO _2$

  3. CO

  4. $CH _4$


Correct Option: A
Explanation:

In the stratosphere of the atmosphere, the UV rays are concentrated and these react with the oxygen to produce the ozone. This ozone persists in the form of the ozone layer and acts as the absorbent for the UV rays. Ozone layer does not allow the UV-B and UV-C from hitting the earth's surface, thereby preventing the various harmful after effects. Sulphur dioxide, carbon monoxide and methane are the primary pollutants of air.

Hence, the correct answer is 'O$ _{3}$'.

Part of ozone is destroyed over poles during

  1. Polar spring

  2. Winter

  3. Summer

  4. Period of snow fall


Correct Option: A
Explanation:

Polar spring, also known as the Antarctic Spring is the period from late August to early October and the strong westerlies circulate around the Antarctic continent creating a polar vortex. The polar vortex results in the formation of the polar stratospheric clouds which trap most of the gases including the ozone-depleting factors like CFCs, methyl bromide etc. 

Hence, the correct answer is 'Polar Spring'.

CFCs split up in stratosphere to release chlorine by the action of

  1. UV - A

  2. UV - B

  3. UV - C

  4. All of the above


Correct Option: C
Explanation:

The UV-C radiations breakdown the bonds in the chlorofluorocarbons (CFCs) to release the chlorine monoxide and the nascent chlorine. These further react with the ozone to split it into ordinary oxygen molecules. The oxygen molecules are further broken down into nascent oxygen, which acts as the radicle. 

Hence, the correct answer is 'UV-C'.

Ozone depletion shall cause higher incidence of

  1. Skin cancers

  2. Cataract

  3. Decreased immunity

  4. All of the above


Correct Option: D
Explanation:

Ozone depletion causes the harmful UV-B radiations to strike the earth surface. These radiations are capable of causing various health issues like malignant skin cancers, cataract, decreased immunity, decreased primary productivity, chlorophyll bleaching etc. 

Hence, the correct answer is 'All of the above'

In the environment, ozone is known for its 

  1. Harmful effects

  2. Useful effects

  3. Both A and B

  4. Inert nature


Correct Option: C
Explanation:

Ozone is an inorganic molecule. It is a pale blue gas with a distinctively pungent smell. In the environment ozone is known for its both harmful and useful effects.
Ozone present in stratosphere is useful as it act like shield and protect the earth from harmful UV-rays which can cause serious problems like skin cancer and decrease in level of photosynthesis. Ozone present in troposphere act as pollutant and have many deleterious effects. 

Therefore, the correct answer is option C.

Ozone hole enhances

  1. UV radiations reaching earth

  2. Number of cataracts

  3. Skin cancers

  4. All of the above


Correct Option: D
Explanation:
The ozone layer is mainly found in the stratosphere. Ozone layer acts as a shield that absorbs ultraviolet radiation from the sun. Due to ozone depletion by the presence of CFC gas the UV rays reaching the earth and causing harmful effects. UV rays are highly injurious to living organisms since DNA and proteins of living organisms preferentially absorb UV rays and its high energy breaks the chemical bonds within these molecules. UV-B damages DNA and mutation may occur. It causes aging of the skin, damage to skin cells and various types of skin cancers. In the human eye, cornea absorbs UV-B radiation, and a high dose of UV-B causes inflammation of the cornea, called as snow-blindness, cataract, etc. Such exposure may permanently damage the cornea. Therefore, the correct answer is option D.

Ozone-layer is getting depleted because of

  1. Excessive use of automobiles

  2. Excessive formation of industrial units

  3. Excessive use of man made compounds containing both fluorine and chlorine

  4. Excessive deforestation.


Correct Option: C
Explanation:

Ozone layer is a region of concentration of ozone molecule. $O _3 (O _2+ O)$ in the earth's atmosphere. The layer lies in the stratosphere at an altitude of 18-50 kms. The ozone layer naturally Shields earth's life from the harmful effect of the Sun's ultraviolet radiations.

Which among the following are the consequences of ozone depletion?

  1. Entry of UV-rays in earth's atmosphere

  2. Various skin troubles like skin cancer

  3. Cataract

  4. All of the above


Correct Option: D
Explanation:

Ozone depletion in the stratosphere has resulted in formation of a large area of thinned ozone layer, commonly called as the ozone hole. UV radiation of wavelengths shorter than UV-B, are almost completely absorbed by Earth's atmosphere, given that the ozone layer is intact. But, UV-B damages DNA and mutation may occur. It causes aging of skin, damage to skin cells and various types of skin cancers. In human eye, cornea absorbs UV-B radiation, and a high dose of UV-B causes inflammation of cornea, called as snow-blindness, cataract, etc. Such exposure may permanently damage the cornea. Thus, the correct answer is option D.

The Hydrochlorofluorocarbons (HCFCs) are the compounds which have the following molecules:HydrogenCarbonChlorineFluorineWhich among the above plays the most important role in Ozone depletion?

  1. Hydrogen

  2. Carbon

  3. Chlorine

  4. Flourine


Correct Option: C

At which of the following places First Global Conference on depletion of Ozone layer was held?

  1. Geneva

  2. Vienna

  3. London

  4. Frankfurt


Correct Option: B

'Nitric acid' reacts with ozone, resulting in removal of

  1. $O{3}$

  2. CO

  3. $CO{2}$

  4. NoX


Correct Option: A

What is involved in ozone depletion?

  1. Chlorofluorocarbons (CFCs)

  2. Carbon tetrachloride (CCl4)

  3. Carbon tetrafluoride (CF4)

  4. All of above


Correct Option: D

Chlorine free radical reacts with 'ozone' to form

  1. CFCs

  2. Chlorine Oxide

  3. $N _{2}$

  4. Bromine Oxide


Correct Option: B

Which chemical is a 'ozone' depleting solvent?

  1. PAN

  2. CFCs

  3. Carbon tetrachloride

  4. Nitrogen


Correct Option: C

Depletion of ozone layer published in scientific journals, in

  1. 1950s

  2. 1990s

  3. 1970s

  4. 1980s


Correct Option: D

What does a single chlorine free radical destroy?

  1. Ultraviolet radiations

  2. Atmosphere

  3. Biosphere

  4. Ozone layer


Correct Option: D

What does high flying crafts deplete?

  1. Atmosphere

  2. Ozone Layer

  3. Biosphere

  4. Hydrosphere


Correct Option: B

Melanornia (skin cancer) is associated with

  1. ozone accumulation

  2. ozone depletion

  3. acid rain

  4. allergens


Correct Option: B

Strong is caused by the _______________.

  1. Depletion of ozone layer

  2. Presence of high humidity in the atmosphere

  3. Rapid accumulation of $CO _2$ in the atmosphere

  4. Rapid build-up of products of photochemical oxidation of pollutants in the atmosphere


Correct Option: A

Multiple Choice Questions
Depletion of which gas in the atmosphere can lead to an increased incidence of skin cancers.

  1. Methane

  2. Nitrous oxide

  3. Ozone

  4. Ammonia


Correct Option: C
Explanation:

Ozone is a triatomic gas that forms a shield or layer in the stratosphere region of atmosphere. This layer protects the living beings from harmful effects of UV-B rays of 280-320 nm. Depletion of the ozone layer can lead to an increased incidence of skin cancer.

So the correct  option is 'ozone'.

Depletion of the Ozone layer in the stratosphere is caused by.

  1. Carbon monoxide

  2. Hydrocarbons

  3. Nitrogen dioxide

  4. Polychloro-biphenyls


Correct Option: A

$O _3$ in ozone layer is formed by action of

  1. IR radiation

  2. Blue radiation

  3. UV radiation

  4. Other radiations


Correct Option: C
Explanation:
Ozone molecule (O3) is formed in the stratosphere in presence of UV radiations.
The first step is the breaking of an oxygen molecule into two oxygen atoms by UV radiation:
                                       UV
                             O3---------------> O + O
The Oxygen atoms then combine with oxygen molecule to form a molecule of ozone:
                           O2 + O -----------------> O3
So, the correct answer is 'UV radiation'.

Nitrogen oxides released in the stratosphere cause ozone depletion due to

  1. Catalysing conversion of ozone to oxygen

  2. Binding ozone

  3. Reacting with ozone

  4. All of the above


Correct Option: C
Explanation:
Nitrogen oxide which causes ozone depletion is Nitrous oxide. It is similar to CFCs in that it is stable when it is released in the troposphere but when it reaches stratosphere, it releases ozone depleting substances which react with ozone and cause its degradation through nitrogen-oxide catalysed reaction.
So, the correct answer is 'Reacting with ozone'. 

Number of ozone depleters identified by Viena convention for Protection of Ozone Layer (1992) is

  1. 19

  2. 17

  3. 15

  4. 13


Correct Option: A
Explanation:
  • The Vienna Convention for the Protection of the Ozone Layer is a multilateral environmental agreement signed in 1985.
  • It provided frameworks for international reductions in the production of chlorofluorocarbons due to their contribution to the destruction of the ozone layer and the resulting increase in the threat of skin cancer.
  • The Number of ozone depleters identified by Viena convention for Protection of Ozone Layer (1992) is 19.
  • So, the correct answer is '19'.

Chlorofluorocarbons are responsible for

  1. Acid rain

  2. Ozone layer depletion

  3. Global warming

  4. Thermal inversion


Correct Option: B
Explanation:

Ozone is found in high concentration in the stratosphere of the earth's surface in the form of ozone blanket or commonly known as the ozone layer. The vital function of ozone is to absorb the sun's ultraviolet radiation before it reaches the ground hence protecting the earth from its harmful effect. But the ozone-depleting substance such as Chlorofluorocarbons, nitrous oxides, etc that reacting with the ozone layer by releasing the reactive chlorine and cause depletion of it forming ozone hole. The concentration of ozone is less than 220 DU in the hole.

Hence, the correct answer is 'Ozone layer depletion'.

Peeling of ozone umbrella is due to

  1. CFCs

  2. PAN

  3. $CO _2$

  4. Coal burning


Correct Option: A
Explanation:

Among the five layers of the earth's atmosphere, ozone is present in the stratosphere which absorbs UV radiation before it reaches the ground. The main cause of ozone depletion is manufactured chemicals especially CFCs, these compounds reach the stratosphere by winds, where they release halogen atoms through photodissociation and cause the breakdown of ozone into oxygen. The ozone hole formed due to this increase the exposure of direct UV rays on earth carrying the potential risk of skin cancer and other negative effects

So, the correct answer is 'CFCs'

Increasing skin cancer and high mutation rate are due to _________.

  1. Acid rain

  2. Ozone depletion

  3. CO pollution

  4. $CO _2$ pollution


Correct Option: B
Explanation:

The ozone layer in the stratosphere is useful because it absorbs the UV radiations from the sun and prevents them from reaching the earth's surface. The depletion of the ozone by the ozone-depleting substances causes the break down of the ozone resulting in the ozone depletion. Due to this, the lives on the earth's surface are exposed to the UV rays. These UV rays induce mutations in the DNA by distorting its structure, leading to the erroneous function and replication of the DNA. The uncontrolled errors at times cause uncontrolled cell proliferation, causing skin cancer.

Hence, the correct answer is 'Ozone Depletion'.

Ozone hole is caused by

  1. Acetylene

  2. Ethylene

  3. Chlorofluorocarbons

  4. Methane


Correct Option: C
Explanation:

Ozone hole refers to the depletion of the ozone layer present in the stratosphere of the atmosphere. The chlorofluorocarbons are the paraffinated halogens that enter the stratosphere with winds and split up when exposed to the UV rays. They release reactive chlorine which further reacts with the ozone to release diatomic oxygen. The ozone hole shows a low concentration of ozone which is less than 220 DU. It is more prominent over Antarctica due to polar vortex and formation of the polar stratospheric clouds.

Hence, the correct answer is 'Chlorofluorocarbons'.

Ozone depletion in stratosphere shall result in.

  1. Forest fires

  2. Increased incidence of skin cancer

  3. Global warming

  4. None of the above


Correct Option: B
Explanation:
Ozone depletion in Stratosphere shall result in infiltration of UV A and UV B rays that would result in increased incidents of skin cancer
So, the correct answer is'Increased incidence of skin cancer'

Chief air pollutant which is likely to deplete ozone layer is ________.

  1. Sulphur dioxide

  2. Carbon dioxide

  3. Carbon monoxide

  4. Nitrogen oxides and fluorocarbons


Correct Option: D
Explanation:

The ozone depleting substances include the chlorofluorocarbons, oxides of nitrogen, methyl bromide, carbon tetrachloride etc because these split up when exposed to UV radiations and release the reactive chlorine and bromine. These reactive species of chlorine and bromine then react with ozone to release the nascent oxygen. Sulphur dioxide and carbon dioxide are greenhouse gases. Carbon monoxide is an air pollutant.

Hence, the correct answer is 'Nitrogen oxides and fluorocarbons'.

ODS means

  1. Ozone developing substance

  2. Ozone depleting substance

  3. Ozone data source

  4. Office data secrecy


Correct Option: B
Explanation:

ODS refers to the ozone-depleting substances like chlorofluorocarbons, methyl bromide, methyl chloroform, carbon tetrachloride, hexaflurocarbons that release the chlorine and oxides of chlorine. These react with the UV rays and ozone to release the nascent oxygen. 

Hence, the correct answer is 'Ozone Depleting Substances'

Ultraviolet radiations from sunlight causes a reaction that produce.

  1. Fluorides

  2. Carbon monoxide

  3. Sulphur dioxide

  4. Ozone


Correct Option: D
Explanation:

Ultraviolet radiations cause photochemical splitting of oxygen molecules in the stratosphere. The nascent oxygen combines with molecular oxygen to form ozone. In troposphere nascent oxygen comes from nitrogen dioxide.

Ozone layer of upper atmosphere is being destroyed by

  1. Chlorofluorocarbon

  2. $SO _2$

  3. Photochemical oxidants/$O _2$ and $CO _2$

  4. Smog


Correct Option: A
Explanation:

Ozone layer is formed in the stratosphere of the atmosphere by the action of UV rays on the oxygen molecules. This ozone layer acts as absorbant for the harmful UV radiations and so, these radiation do not cross the troposphere to reach the earth's surface. However, the ozone depleting pollutants like chlorofluorocarbons reach the stratosphere and break when exposed to the UV rays. This process releases the reactive chlorine which further reacts with ozone to form simple oxygen. That is how the ozone layer is depleted. Hence, the correct answer is 'Chlorofluorocarbons'.

Pollutant likely to deplete ozone layer is?

  1. CO

  2. Nitrogen oxides

  3. Chlorofluorocarbons

  4. Both B and C


Correct Option: D
Explanation:
  • Nitrous oxide is stable at ground level and breaks down when it reaches the stratosphere to form nitrogen oxides, that trigger ozone-destruction
  • The main cause of ozone depletion are halocarbon refrigerants, such as chlorofluorocarbons (CFCs), HCFCs, halons).
  • So, the correct option is 'Both B and C'.

Which type of electron is present in free radical?

  1. Unpaired and extremely reactive

  2. Paired and extremely inactive

  3. Unpaired and extremely inactive

  4. Paired and extremely reactive


Correct Option: A
Explanation:

Free radicals have unpaired electrons. These are extremely reactive. As one chlorine free radical can remove 11000 ozone molecules from stratosphere.

The Pollutant responsible for Ozone depletion is 

  1. $CFCs$

  2. $MIC$

  3. $CO _2$

  4. $SO _2$


Correct Option: A

Which one of the following diseases is caused due to ozone depletion on human?

  1. Huntington's chorea

  2. Small pox

  3. Plague

  4. Erythemia


Correct Option: D
Explanation:
  • Due to the ozone depletion, the UV rays are filtered in the Earth's atmosphere. 
  • This ray results in the development of various diseases. One of the common disorder is erythema. 
  • This is a disease in which there are reddening and swelling of the skin. There is swelling of the mucous membranes. 
  • There is an increase in the blood flow from the peripheral capillaries which results in inflammation.
  • Thus, the correct answer is option D. 

Which one of the following gases can deplete ozone layer in the upper atmosphere?

  1. Ammonia

  2. Methane

  3. Carbon monoxide

  4. None of the above


Correct Option: B
Explanation:
Methane can deplete ozone layer in the upper atmosphere. It acts as a greenhouse gas (a gas that traps heat from the sun within earth’s atmosphere) and it also attacks ozone. At low latitudes, methane in the stratosphere breaks down into hydrogen oxides, which attack reaching the ozone layer reacts with it and leads to the splitting of bonds between ozone.
So, the correct answer is option B.

Which one of the following chemicals is responsible for the reduction of ozone content of atmosphere?

  1. Hydrochloric acid

  2. Photochemical smog

  3. Chlorofluorocarbon (CFC)

  4. Sulphur dioxide


Correct Option: C
Explanation:

Chlorofluorocarbons or Chlorofluoromethane are also known as freon or aerosols. They are chemicals used as refrigerants, propellants and solid plastic foams. These chemicals are also released as aerosols by jets flying at high altitudes. Along with nitrogen oxides, chlorofluorocarbons react with ozone of ozonosphere and depletes the same. Chlorofluorocarbons release reactive chloride which directly reacts with ozone molecules setting a chain reaction.

Good ozone is found in 

  1. Atmosphere

  2. Biosphere

  3. Stratosphere

  4. Ozonosphere


Correct Option: C
Explanation:

The correct answer is Stratosphere. Option C

Ozone occurs in the Earth's upper atmosphere—10 to 30 miles above the Earth's surface and protects from the sun's harmful ultraviolet (UV) rays Stratospheric ozone is formed naturally by chemical reactions involving solar ultraviolet radiation (sunlight) and oxygen molecules.

Ozone in the stratosphere is depleted by

  1. $C _6F _6Cl _6$

  2. $C _7F _{16}$

  3. $CF _2Cl _2$

  4. $C _6F _6$


Correct Option: C
Explanation:

The presence of CFCs in the atmosphere results in the depletion of the ozone layer. The chemical formula of this substance is CF$ _2$Cl$ _2$. They are used as coolants in refrigerators, coolers, etc. The CFCs causes the breaking of the ozone molecule which forms the oxygen radical and O$ _2$. The depletion of the ozone layer results in the penetration of the harmful UV radiations from the sun into the Earth's atmosphere. 

Thus, the correct answer is option C. 

Which of the following is the result of use of chlorofluorocarbons?

  1. Global warming

  2. Eutrophication of lates

  3. Depletion of the ozone layer

  4. Magnification in the food chain

  5. Acid rain


Correct Option: C
Explanation:

A chlorofluorocarbon (CFC) is composed of carbon, chlorine, and fluorine. This is used in refrigerants, propellants, and solvents. The chlorine atoms are released due to splitting of CFC by ultravoilet radiation.

So, the correct answer is option C.

Chlorofluorocarbons cause

  1. Global warming

  2. Eutrophication of lakes

  3. Depletion of the ozone layer

  4. Magnification in the food chain

  5. Acid rain


Correct Option: C
Explanation:
Chlorofluorocarbons (CFC) also known as freons which cause a destruction of ozone layer found in the stratospheric layer. The ozone layer in the atmosphere prevents the harmful UV rays from reaching the earth surface. When this ozone layer gets depleted, harmful UV rays causes skin cancer. 

Destruction of ozone can cause 

  1. Skin cancer

  2. Cataract

  3. Hinder growth of plant

  4. All of these


Correct Option: D
Explanation:

Destruction of ozone can cause skin cancer, cataract and can hinder growth of plant. Ozone prevents the harmful radiations from reaching the surface of earth. The UV radiation has enough energy to cause adverse effects on all life systems, especially humans. It can destroy parts of DNA molecules that stores and propagate genetic information from one generation to another generation.

Depletion of ozone layer is mainly due to

  1. Methane

  2. Carbon dioxide

  3. Chloroflorocarbons

  4. Nitrogen


Correct Option: C
Explanation:

Depletion of ozone layer is mainly due to Chloroflorocarbons.
Note:
The following describes the destruction of the ozone by chlorofluorocarbons.
Chlorofluorocarbons contains the chlorine molecule which reacts with ozone (O$ _3$) molecule and splits into O$ _2$ and O molecules.
Chlorofluorocarbons are used in refrigerators, air conditioners and aerosol sprays. They damage the ozone layer of the atmosphere.

40 to 50% depletion in ozone layer occurs in the .......... polar region

  1. North

  2. South

  3. East

  4. West


Correct Option: B
Explanation:

40 to 50% depletion in ozone layer occurs in the South polar region.
Ozone is destroyed by collisions with other atoms and molecules.
The large scale destruction of the stratospheric ozone first came into focus in 1987 through the experiments in antarctica.

_____ shields the surface of the earth from ultraviolet (UV) radiation from the sun.

  1. Oxygen

  2. Nitrogen

  3. Ozone

  4. Carbon dioxide


Correct Option: C
Explanation:

Ozone shields the surface of the earth from ultraviolet (UV) radiation from the sun. Ozone layer reduces the chances of skin cancer.

Which of the following conditions lead to formation of ozone?

  1. When oxygen molecules absorb ultraviolet photons and undergo photolysis

  2. When carbon molecules absorb ultraviolet photons and undergo photolysis

  3. When oxygen molecules absorb ultraviolet electrons and undergo photolysis

  4. When oxygen molecules absorb ultraviolet neutrons and undergo photolysis


Correct Option: A
Explanation:


When oxygen molecules absorb ultraviolet photons and undergo photolysis, ozone is obtained
$3O _2 \xrightarrow [photolysis]{UV : light} 2O _3$.

Ozone is found in the atmosphere and helps to protect us from harmful radiation. Ozone is

  1. $\displaystyle { O }^{ 2- }$

  2. $\displaystyle { O }^{ - }$

  3. $\displaystyle \ { O } _{ 2 }\ $

  4. $\displaystyle \ { O } _{ 3 }\ $


Correct Option: D
Explanation:

Ozone is an inorganic molecule formed by the three molecules of oxygen with the chemical formula O$ _3$. It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope O$ _2$ and more reactive molecule.

The ozone layer: Between 15 and 50 km above the earth is a thin layer of gas called 'ozone'. It protects the earth from most of the sun's harmful ultraviolet radiation. Too much radiation causes blindness in animals and skin cancer in people. In 1985, scientists discovered a hole in the ozone layer in the Antartica. They have recently discovered a smaller hole over the arctic. The ozone layer is also becoming thinner over other locations of the earth too. Scientists believe that over the last 10 years about 30% of the ozone layer has disappeared. This damage is caused by chemicals. Choose the right statement(s) from the following. 

  1. The greenhouse effect would be more efficient and the temperature of earth would increase.

  2. CFCs would result in the depletion of the ozone layer.

  3. Infrared radiation from the sun would bombard earth.

  4. Ultraviolet radiation from the sun cannot enter earth.


Correct Option: B
Explanation:

The presence of CFCs in the atmosphere results in the depletion of the ozone layer. They are used as coolants in refrigerators, coolers, etc. The CFCs causes the breaking of the ozone molecule which forms the oxygen radical and O$ _2$. The depletion of the ozone layer results in the penetration of the harmful UV radiations from the sun into the Earth's atmosphere. 

Thus, the correct answer is option B. 

The factor responsible for depletion of ozone layer is

  1. Excessive use of automobiles

  2. Excessive industrial units

  3. Excessive use of man made compounds containing chlorine and fluorine

  4. Excessive deforestation


Correct Option: C
Explanation:

Chlorofluorocarbon compounds are released from automobiles, refrigerators, etc. These compounds cause an increase in atmospheric temperature causing global warming.

So, option C " Excessive use of man-made compounds containing chlorine and fluorine" is the correct answer.

Increase skin cancer and higher mutation rates are generally the consequences of

  1. CO$ _2$

  2. Ozone depletion

  3. Biomagnification

  4. Acid rains


Correct Option: B
Explanation:

The ozone layer is present in the stratosphere above the Earth. The layer of ozone is responsible for the absorption of the harmful ultraviolet radiations from the solar radiations. Due to ozone depletion, these radiations enter the Earth's atmosphere and cause skin cancer. The radiations can also damage the eye and other exposed parts of the body. The radiations can also cause mutations like thymine dimer formation or breaking of the hydrogen bonds. 

Thus, the correct answer is option B. 

Which of the following chemical is released by chlorofluorocarbon that is harmful to ozone ?
  1. Fluorine

  2. Sulphur dioxide

  3. Nitrogen peroxide

  4. Chlorine


Correct Option: D
Explanation:

Chlorofluorocarbons are the compounds which are used as coolants in the air conditioning systems, refrigerators, coolers, etc. The CFCs, when released into the atmosphere, react with UV rays to form chlorine atoms which destroy the ozone layer and results in the thinning out of the ozone layer also known as the ozone hole.

Thus, the correct answer is option D. 

CFCs used in refrigerators cause 

  1. Water pollution

  2. Ozone depletion

  3. Acid rain

  4. Photochemical smog


Correct Option: B
Explanation:

The presence of CFCs in the atmosphere results in the depletion of the ozone layer. They are used as coolants in refrigerators, coolers, etc. The CFCs causes the breaking of the ozone molecule which forms the oxygen radical and O$ _2$. The depletion of the ozone layer results in the penetration of the harmful UV radiations from the sun into the Earth's atmosphere. 

Thus, the correct answer is option B. 

The common refrigerant chlorofluoromethane (freon) and NO$ _x$ is a serious pollutant because

  1. It destroys haemoglobin

  2. It disrupts O$ _3$ layer

  3. It lowers atmospheric temperature

  4. It prevents cloud condensation


Correct Option: B

Ozone layer is disturbed by

  1. Large number of factories

  2. Supersonic jets

  3. Large number of automobiles

  4. None of these


Correct Option: B
Explanation:
Ozone is a form of a blanket covering the upper atmosphere which protects the earth from harmful ultraviolet rays. Because of ozone depletion, these rays can now reach the earth through hole which was previously protected by ozone blanket. The various causes of ozone depletion are as follows:
  • Huge combustion of fossil fuel and organic matter.
  • Excessive use of nitrogenous fertilizers.
  • supersonic rockets and space shutters.
  • Nuclear test.
  • Excessive use of chlorofluorocarbons.
So, the correct answer is option B.

Chlorofluorocarbon releases a chemical harmful to ozone

  1. Fluorine

  2. Sulphur dioxide

  3. Nitrogen peroxide

  4. Chlorine


Correct Option: D
Explanation:

Ozone gas is a layer which is present in the stratosphere and absorbs the harmful ultraviolet radiation. The ozone depletion takes due to the excessive emission of (CFCs). CFC find wide use as refrigerants. CFCs discharged in the lower part of atmosphere move upward and reach stratosphere. In stratosphere, UV rays act on them releasing Cl atoms. Cl degrades ozone releasing molecular oxygen, with these atoms acting merely as catalysts; Cl atoms are not consumed in the reaction. Hence, whatever CFCs are added to the stratosphere, they have permanent and continuing affects on ozone levels. This has resulted in formation of a large area of thinned ozone layer, commonly called as the ozone hole.

Therefore, the correct answer is option D.

Ozone protects biosphere from high energy

  1. Infra-red rays

  2. Ultraviolet rays

  3. X - rays

  4. Gamma rays


Correct Option: B
Explanation:

The ozone layer is mainly found in the stratosphere. Ozone layer acts as a shield that absorbs ultraviolet radiation from the sun. UV rays are highly injurious to living organisms since DNA and proteins of living organisms preferentially absorb UV rays, and its high energy breaks the chemical bonds within these molecules. UV-B damages DNA and mutation may occur. It causes aging of the skin, damage to skin cells and various types of skin cancers.

Ozone layer of upper atmosphere is being destroyed by 

  1. Sulphurdioxide

  2. Carbondioxide

  3. Chlorofluorocarbon

  4. Smog


Correct Option: C
Explanation:
CFCs are used as refrigerants in refrigerators and AC. CFCs discharged in the lower part of atmosphere move upward and reach the stratosphere. In the stratosphere, UV rays act on them releasing Cl atoms. Cl reduces the ozone and releases molecular oxygen, Cl atoms are not consumed in the reaction. Hence, whatever CFCs are added to the stratosphere, they have permanent and continuing effects on ozone levels. This has resulted in the formation of a large area of thinned ozone layer, commonly called as the ozone hole.

The major pollutants to deplete ozone are

  1. Chlorofluorocarbons

  2. Nitrogen oxides

  3. Hydrocarbons

  4. All of the above


Correct Option: A
Explanation:

Pollution leads to the addition of harmful components in the environment which adversely affect the quality of the environment. CFCs is an organic compound and a volatile derivative of methane, ethane, and propane. It is known as Freon. They are used as a refrigerant. The radical chlorine escapes from CFC in the presence of UV radiation and is long lived in the upper atmosphere where it catalyzes the conversion of ozone into oxygen molecule.

So, the correct answer is option A.

Ozone depletion is occurring due to 

  1. PCB

  2. CO

  3. PAN

  4. None of the above


Correct Option: D
Explanation:

Ozone is the protective layer present in the stratosphere. The harmful ultraviolet radiation is absorbed by the ozone layer. They are carried high into the stratosphere by wind action. Depletion begins when CFC’s get into the stratosphere. Ultraviolet radiation from the sun breaks up these CFCs. The breaking up action releases chlorine atoms. Chlorine atoms react with ozone, starting a chemical cycle that destroys the good ozone in that area. It is not depleted by PCB, carbon monoxides, and PAN. 

Therefore, the correct answer is option D.

Which among the following alkane has largely replaced the ozone layer-depleting halomethanes in household refrigerators and freezers?

  1. Methane

  2. Propane

  3. Butane

  4. Ethane


Correct Option: C

HCs are thermodynamically not stable towards

  1. Acidification

  2. Decomposition

  3. Reduction

  4. Oxidation


Correct Option: D

'HCFCs' can be used in refrigerants instead of

  1. $CO _{2}$

  2. Chlorine

  3. CFCs

  4. $O _{2}$


Correct Option: C

What causes effects of ozone layer?

  1. Alpha Radiations

  2. Ultraviolet Radiations

  3. Gamma radiations

  4. Beta Radiations


Correct Option: B

What gases are involved in ozone depletion?

  1. Nitrogen

  2. Chlorine and Bromine

  3. Chlorofluorocarbons (CFCs) and Ozone Depleting Substances (ODS)

  4. Both B and C


Correct Option: B

Major cause of Ozone depletion is due to which chemical?

  1. Chloro Fluoro Carbons

  2. Polyphenols

  3. Dioxins

  4. Rayon


Correct Option: A

The effect of ozone depletion include

  1. UV light reaches the earth

  2. affect the climate

  3. cause skin cancer

  4. all the above


Correct Option: D

_____________ is the first country to have phased out the CFCs and HCFCs which are responsible for the depletion of the ozone layer

  1. Denmark

  2. Germany

  3. France

  4. Spain


Correct Option: B

Why ozone is known as 'chemical weed ' ?

  1. Because it is formed by chemical reactions

  2. Because it is harmful as well useful

  3. Because it is harmful, just like weeds for mankind

  4. Ozone is not designated as chemical weed


Correct Option: A
Explanation:

Ozone is an inorganic molecule and a light blue gas with a pungent odor that is prevalent in the stratosphere just below the atmosphere of the earth. Without ozone, plants and animals would be receiving so much radiation from the sun that it would be difficult, if not impossible, for life to even survive here. The effects of no ozone to protect these harmful rays would be that all life here on earth would soon burn up, essentially. Although most associated with the atmosphere, ozone is also a powerful oxidant with many industrial and consumer uses. However, it must be used with extreme caution. The high oxidizing potential of ozone causes damage to mucous and respiratory tissues in animals and also damages tissue in plants at extremely high levels. In commercial agriculture, ozone can be used in conjunction with other chemicals and gases as a control for certain noxious weeds or pests.


So, the correct option is 'Option A', Because it is formed by chemical reactions.

Which harmful radiations are absorbed by ozen layer?

  1. UV

  2. X-RAY

  3. Visible light

  4. Gamma rays


Correct Option: A
Explanation:
  • The ozone layer or ozone($O _3$) shield is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet(UV)radiation.
  • Overexposure to UV radiation may cause skin cancer, damage of the eye and the suppression of the immune system.
  • Hence The harmful radiations are absorbed by ozone layer UV.
  • So, the correct answer is 'UV'.

Ozone layer depletion may lead to which of the following harmful effects in organisms?

  1. Skin cancer

  2. Cataract

  3. Damage to the immune system

  4. All of the above


Correct Option: D
Explanation:

Ozone gas is found in the stratosphere of the atmosphere. The ozone layer protects the earth from the harmful ultraviolet rays emitted from the sun. Ozone layer depletion has many adverse serious environmental effects. It may result in global warming. The ultraviolet radiations exposure leads to skin cancer like malignant melanoma. It also increases the rate of ageing in an individual. It also has harmful effect on the eyes. It may cause cataract. Immune system is also affected by this harmful ultraviolet radiations. Apart from humans, ozone layer depletion affects marine, aquatic and other forms of life as well.

Thus, the correct answer is 'All of the above.'

Which of the following are main responsible for ozone depletion?

  1. Chlorofluorocarbons

  2. Hydrocarbons

  3. Carbon monoxide

  4. Carbon dioxide


Correct Option: A
Explanation:
  • Ozone depletion occurs when chlorofluorocarbons (CFCs) present in aerosols and refrigerants are released into the stratosphere. 
  • Ultraviolet radiations from the sun break these CFCs molecules and release the chlorine atoms.
  • Chlorine atom reacts with the ozone (O3) molecules and starts the ozone destruction cycle.
  • So, the correct answer is 'Chlorofluorocarbons'.

Excessive exposure of humans to UV-rays results in

  1. damage to immune system

  2. damage to lungs

  3. skin cancer

  4. peptic ulcers


Correct Option: A,C
Explanation:
UV rays or ultraviolet rays can affect human health in many ways like causing skin cancer and a weakening immune system. Excessive exposure to UV rays can lead to skin cancer because the UV rays cause damage to the DNA in skin cells. UV rays also affect the distribution and activity of cells that trigger immune responses thus, making the immune system weak. UV rays first affect the skin and the whole body.
So, the correct answer is option A and C i.e. 'damage to immune system' and 'skin cancer'.

Maximum ozone depletion is caused by

  1. $CO _2$

  2. CFC

  3. $SO _2$

  4. $CH _4$


Correct Option: B
Explanation:
The primary cause for ozone depletion are CFCs. CFCs or Chlorofluorocarbons are the compounds that contain carbon and hydrogen along with chlorine and fluorine. They are used as refrigerants and in air conditioners. CFCs release chlorine radicals that react with ozone and cause its degradation. The mechanism of ozone depletion by CFC is as follows:
              UV- C
CFCl3 ----------------> CFCl2 + Cl
               UV-C
CFCl2 -----------------> CFCl + Cl
Cl + O3 ----------------> ClO + O2
ClO + O3 --------------> Cl + 2O2
Hence, CFC causes degradation of ozone. Also, the chlorine atom remains in the atmosphere and reacts with another molecule of ozone.
So, the correct answer is 'CFC'.

Freon gas causing stratosphere $O _3$ depletion is mainly released from

  1. Refrigerators

  2. Automobiles

  3. Thermal power plants

  4. Steel industry


Correct Option: A
Explanation:
Freon gas is a type of chlorofluorocarbon (CFC) i.e., it contains carbon and hydrogen along with fluorine and chlorine. It is used as a refrigerant. CFCs release chlorine atoms in the atmosphere that react with ozone and cause its depletion. Hence, Freon causes ozone depletion and it is released from refrigerators.
So, the correct answer is 'Refrigerators'.

Of the following, which is a greenhouse gas?

  1. Nitrogen dioxide

  2. Sulphur dioxide

  3. Carbon dioxide

  4. Carbon monoxide


Correct Option: C
Explanation:
Greenhouse gases generally traps the radiations of the earth which leads to increase in the temperature of the earth and is the major cause for global warming. The greenhouse gases includes water vapour, carbon dioxide, methane, nitrous oxide, and ozone.
Thus, the correct answer is option C.

In coming years, skin related disorders will be more common due to:

  1. Pollutants in air

  2. Use of detergents

  3. Water pollution

  4. Depletion of ozone layer


Correct Option: D
Explanation:

Thinning of ozone layer increases the amount of ultraviolet radiations reaching the earth surface. The increased UV-B radiation increases incidence of cataract, skin cancers herpes, dimming of eyesight, photo burning, snow blindness and deficient functioning of immune system. 

The stratospheric ozone depletion leads to

  1. Global warming

  2. Increase in the incidence of skin cancers

  3. Forest fires

  4. All of the above


Correct Option: D
Explanation:
Thinning of ozone layer increases the amount of UV-B radiations reaching the earth. This may lead to incidences of cataract, skin cancers, photo burning etc. Decreased photosynthetic activity will increase carbon dioxide concentration of the atmosphere resulting in global warming. Increased exposure of radiations may also lead to forest fires especially during dry summers.
So, the correct answer is 'All of the above'

The reduction in the amount of chlorofluorocarbons (CFCs) released into the air has had the greatest positive effect upon 

  1. Water pollution 

  2. Noise pollution

  3. Acid rain 

  4. The ozone layer

  5. Endangered species


Correct Option: D
Explanation:

The presence of CFCs in the atmosphere results in the depletion of the ozone layer. They are used as coolants in refrigerators, coolers, etc. The CFCs causes the breaking of the ozone molecule which forms the oxygen radical and O$ _2$. The depletion of the ozone layer results in the penetration of the harmful UV radiations from the sun into the Earth's atmosphere. The reduction in the use of the CFC molecules will prevent the ozone thinning and have the positive effect on the ozone layer. 

Thus, the correct answer is option D. 

Identify the harmful radiations emitted by the sun.

  1. Ultra violet

  2. Infra red

  3. Visible

  4. Radio waves


Correct Option: A
Explanation:

The ultraviolet radiations are the harmful rays which are present in the sun rays. The radiations are emitted from the sun and are harmful to living organisms. The ozone layer prevents the entry of these radiations into the Earth's atmosphere. The depletion of the ozone layer allows the radiations to cause harm to the plants and animals on the Earth.

Thus, the correct answer is option A. 

Ozone is present as a chief constituent in which region of the atmosphere?

  1. Troposphere

  2. Stratosphere

  3. Mesosphere

  4. Thermosphere


Correct Option: B
Explanation:
The stratosphere is a second layer of Earth's atmosphere. The troposphere, the lowest layer, is right below the stratosphere. The next higher layer above the stratosphere is the mesosphere.
Ozone is a three oxygen molecule that are abundant in the stratosphere, it absorbs energy from incoming ultraviolet radiation from the Sun. 

What happen when the destruction of the ozone layer increases?

  1. The amount of harmful ultraviolet radiation

  2. The amount of needful ultraviolet radiation

  3. The amount of ultra radiations

  4. None of these


Correct Option: A
Explanation:

When the destruction of the ozone layer increases, the amount of harmful ultraviolet radiation increases.
Note:
Ozone layer acts as natural sun block and shields us from the UV radiations of the sun which are dangerous to living organisms.
The ozone molecules absorb ultraviolet rays between 310 to 200 nm wavelength.
Ozone absorbs UV radiation to give back oxygen. Thus, the ozone layer acts as a screen and prevents the harmful radiations from reaching the surface of earth.

UV light radiation cause

  1. Formation of pyrimidines

  2. Photodynamic action

  3. Breakage of hydrogen bonds in DNA

  4. Protein denaturation


Correct Option: C
Explanation:

The UV radiations can cause mutation in the cells by altering the DNA. These are ionising radiations which can damage the structure of the DNA molecule. The UV rays can result in the formation of thymine dimers or split the hydrogen bonding. This results in distortion in the structure of DNA and the cell dies due to malfunctioning of the genetic material. 

Thus, the correct answer is option C. 

Maximum threat to the world is from

  1. Global warming

  2. Ozone hole

  3. Water pollution

  4. Soil erosion


Correct Option: B
Explanation:

Maximum threat to the world is from ozone layer which is found in the stratosphere. This layer acts as a shield absorbing UV radiations from the sun. For the ozone layer to be intact there has to be a balance between the production and degradation which has been disturbed by the CFCs used in refrigerators. The F and Cl, which are released by these compounds results in the thinning out of the ozone layer also known as the ozone hole. It causes threat to life and environment as it leads to skin aging and cancers, snow blindness, cataract, melting of polar ice caps, global warming etc.

So, the correct answer is 'Ozone hole'

In which of the following year, the depletion of the ozone layer have been noticed?

  1. 1979

  2. 1980

  3. 1981

  4. 1982


Correct Option: B
Explanation:

The depletion of the ozone layer was noticed in the year 1980.
The large scale destruction of the stratospheric ozone first came into focus in 1987 through the experiments in antarctica.

The main factor responsible for the depletion of ozone layer is addition of _____in the atmosphere.

  1. $Mn$

  2. $Cl$

  3. $Na$

  4. $Co$


Correct Option: B
Explanation:

The main factor responsible for the depletion of ozone layer is addition of Cl in the atmosphere.
Each Cl atom can destroy as many as 100,000 ozone molecules. Cl atoms comes from chlorofluorocarbons.

The ozone layer in earth's atmosphere is crucial for human survival because it

  1. Has ions

  2. Reflects radio signals

  3. Reflects ultraviolet rays

  4. Reflects infrared rays


Correct Option: C
Explanation:

An ozone layer, present in the stratosphere, reflects the ultraviolet rays emitted by the sun and thus it prevents us from skin diseases and mutation.

So, the correct answer is option C.

The maximum hole of ozone is found over ______

  1. Arctic zone

  2. Antarctic zone

  3. Tropical zone

  4. Subtropical zone


Correct Option: B
Explanation:
Ozone-depleting substances are present throughout the stratospheric ozone layer because they are transported great distances by atmospheric air motions. The severe depletion of the Antarctic ozone layer known as the “ozone hole” occurs because of the special atmospheric and chemical conditions that exist there and nowhere else on the globe. The very low winter temperatures in the Antarctic stratosphere cause polar stratospheric clouds (PSCs) to form. Special reactions that occur on PSCs, combined with the relative isolation of polar stratospheric air, allow chlorine and bromine reactions to produce the ozone hole in Antarctic springtime. 
So, the correct answer is 'Antarctic zone'.

Increasing skin cancer and high mutation rate are the result of _______________.

  1. Ozone depletion

  2. Acid rain

  3. $CO$ pollution

  4. $ { CO } _{ 2 } $ pollution


Correct Option: A
Explanation:

Ozone depletion occurs widely in the stratosphere due to an increased amount of $ { CFC }{ s } $ which causes various types of skin cancer and mutations.

So, The correct answer is (A)- Ozone depletion.

Ozone depletion is occurring widely in ______________.

  1. Troposphere

  2. Stratosphere

  3. Ionosphere

  4. All of these


Correct Option: B
Explanation:

Ozone depletion is occurring widely in the stratosphere, particularly marked over the Antarctic region.

So, The correct answer is (B)- Stratosphere.

The major ozone depleting substance out of the following is _____________.

  1. $ { CFC }{ s } $

  2. $ { O } _{ 2 } $

  3. Nitrogen

  4. All of these


Correct Option: A
Explanation:

Ozone-depleting substances (ODS) are substances that react with ozone present in the stratosphere and destroy the same. The major Ozone-depleting substances are chlorofluorocarbons (14% of total depletion), nitrogen oxides (3.5% depletion), sulphur dioxide, halon, carbon tetrachloride, methyl chloroform, chlorine, etc.

Read the following statements and select the correct option.


Statement 1: Ozone layer present in the stratosphere protects the living organisms from harmful UV rays coming from the sun by absorbing nearly all of them.

Statement 2: Ozone formed in the troposphere by photochemical reactions as a result of human activities which is harmful to all living organisms.

  1. Both statements 1 and 2 are correct.

  2. Statement 1 is correct but statement 2 is incorrect.

  3. Statement 1 is incorrect but statement 2 is correct.

  4. Both statements 1 and 2 are incorrect.


Correct Option: A
Explanation:

'Good ozone' is found in the upper part of the atmosphere called the stratosphere and it act as a shield by absorbing ultraviolet radiations from the sun. UV rays are, highly injurious to living organisms. 'Bad ozone' is formed in the lower part of atmosphere called troposphere and it harms plants and animals.

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