Physics · Science General

Optics and Light Properties

2,013 Questions

Optics and light properties focus on the behavior of light, including reflection, refraction, dispersion, and polarization. This topic also covers the wave nature of light, illumination, and the functioning of optical instruments like microscopes. Questions on these concepts are common in general science sections of SSC, Railways, and State exams.

Reflection and mirrorsRefraction and mediumsLight wave theoriesPolarization and intensity

Optics and Light Properties Questions

Multiple choice physics refraction of light the nature of light speed of light and optical density introduction to light

When a ray of light enters glass from water, it bends :

  1. Away from the normal due to increase in the speed of light

  2. Away from the normal due to decrease in the speed of light

  3. Towards the normal due to decrease in the speed of light.

  4. Towards the normal due to increase in the speed of light.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

When a ray of light enters from glass to water, it bends towards normal due to increase in speed of light. 

As we know,

          $\mu=\dfrac{c}{v}$

         $\mu$ for water is less than that of glass, as glass acts as a denser medium. $\therefore$ the speed of light in glass will be less than that in water.

Multiple choice stefan's law black body radiation heat transfer thermal properties physics

If a graph is plotted by taking spectral emissive power along $y-$axis and wavelength along x-axis is:

  1. Emissivity

  2. Total intensity of radiation

  3. Diffusivity

  4. Solar constant
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Emissive power varies according to Stefan-Boltzmann law as :

$E=\sigma {{T}^{4}}$

According to Planck’s distribution law:

${{E} _{\lambda }}(\lambda ,T)=\dfrac{{{C} _{1}}}{{{\lambda }^{5}}\left[ \exp (\dfrac{{{C} _{2}}}{\lambda T})-1 \right]}$

The graph shows that the emitted radiation varies with wavelength and also it shows Emissivity.

 

Multiple choice chemistry solid state classification of crystalline solids classification of solids introduction to solids

Metallic solids are always opaque because:

  1. they reflect all the incident light

  2. they scatter all the incident light

  3. the incident light is readily absorbed by the free electrons in a metal

  4. the energy band traps the incident
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Metals are opaque because they have metallic bonding which means that all of the atoms are surrounded by free-moving electrons.


The incident light on metals is absorbed by large numbers of available free electrons in metals to increase their kinetic energy and hence they are opaque.

Multiple choice physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

Choose the correct answer from the alternatives given.
Radio waves diffract around building although light waves do not. The reason is that radio waves

  1. travel with speed larger than c

  2. have much larger wavelength than light

  3. are not electromagnetic waves

  4. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$Answer:-$ B

Both radio and light waves are EM waves, just in different frequency ranges. The wavelength of visible light is typically around the 600 nm range, which is 6/1000 of a millimeter (very small!). Radio waves on the other hand, often wave wavelengths of a few yards long. For a wave to diffract around an object, the size of the object must be on the same order of the wavelength of the wave.

Multiple choice physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

Choose the correct answer from alternatives given.
The phenomena involved in the reflection of radio waves by ionosphere is similar to

  1. reflection of light by a plane mirror.

  2. total internal reflection of light in air during a mirage.

  3. dispersion of light by water molecules during the formation of a rainbow.

  4. scattering of light by the particles of air.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The phenomenon involved in the reflection of radiowaves by ionosphere is similar to total internal reflection of light in air during a mirage (angle of incidence gt critical angle). It is same as the formation of the rainbow because it also involves the process of total internal reflection.


Choice $(b)$ is correct.

Multiple choice physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

Fluorescent tubes give more light than a filament bulb of same power because

  1. the tube contains gas at low temperature

  2. ultraviolet light is converted into visible light by fluorescence

  3. light is diffused through the walls of the tube

  4. it produces more heat than bulb
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The tubelight has coating of fluorescent material which converts ultra violet light into visible light. Hence the light is more intense. 

Multiple choice physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

 Which one of waves tans our skin and causes some substances to become fluorescent?

  1. infrared waves.

  2. ultraviolet waves.

  3. gamma rays.

  4. infrared and ultraviolet waves both.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Ultraviolet rays (or waves) tan our skin and cause some substances to become fluoroseun sun is important source of ultraviolet light. Sun rays reach our skin and burns the upper layer of skin, causing sunburns prolonged doses of UV radiation can induce skin cancer in human beings.

Ozone layer is protecting us from UV rays but the problem is that Ozone layer is also depleting because of excessive use of CFC's.

Multiple choice physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

X - ray beam can be deflected by 

  1. Magnetic field

  2. Electric field

  3. Both (a) & (b)

  4. None of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$X-$rays aren't deflected by electrons and magnetic fields because $x-$rays do not carry and charge. They are electro-magnetic radiations and therefore cannot be deflected by electronic or any magnetic fields.

Multiple choice physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

When accelerating voltage is increased from $10\ kV$ to $20\ kV$ in an X-ray tube, the gap between the wavelengths of $K _{\alpha}$ line and lowest end of continuous spectrum increases three times. The atomic number of the target element is:-

  1. $29$
  2. $27$
  3. $25$
  4. $23$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The shortest wavelength of the continuous spectrum is lambda_min = hc / eV. The gap between K-alpha and lambda_min is related to the accelerating voltage. Using Moseley's law and the given conditions, the atomic number Z can be solved.

Multiple choice physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

A beam of electrons accelerated by a large potential difference $V$ is made to strike a metal target to produce $X-$rays. For which of the following values of $V$, the resulting $X-$rays have the lowest minimum wave length:

  1. $10\ KV$
  2. $20\ KV$
  3. $30\ KV$
  4. $40\ KV$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

As we know, $\boxed{E _{max}=\dfrac{hc}{\lambda _{min}}}$

$\boxed{\lambda _{min}=\dfrac{hc}{ev}}$
Here the value of $v$ is given as $10kv,20kv,30kv,40kv$
A, $\boxed{\lambda \propto \dfrac{1}{V}}$, large value of $V$
$\Rightarrow$ min. value of $\lambda$
Hence for $40kv$, $\lambda _{min}$ is minimum.
$\therefore$ option $D$ is correct.