Tag: physics

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Questions Related to physics

Multiple choice physics range of hearing sound: production of sound audible, infrasonic and ultrasonic sounds different sounds

A person moving in a car with a velocity of $36kmph $ towards a fort wall blows a horn. If he hears the echo after $3s$, the distance of the wall from him. when he blows then horn (velocity of sound $340ms^P{-1}$)

  1. $340m$

  2. $1050m$

  3. $700m$

  4. $525m$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The sound travels to the wall and back. Let d be the distance when the horn is blown. The wall is stationary. The sound travels distance d + (d - v_car * t) = 2d - v_car * t. 2d - v_car * t = v_sound * t. 2d = (v_sound + v_car) * t. v_car = 36 km/h = 10 m/s. 2d = (340 + 10) * 3 = 350 * 3 = 1050. d = 525 m.

Multiple choice physics range of hearing sound: production of sound audible, infrasonic and ultrasonic sounds different sounds

Bats detect the obstacles in their path by receiving the reflected

  1. infrasonic waves

  2. ultrasonic waves

  3. micro waves

  4. radio waves
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Answer is B.

Most bats produce echolocation sounds by contracting their larynx (voice box). A few species, though, click their tongues. These sounds are generally emitted through the mouth. Echolocation calls are usually ultrasonic, ranging in frequency from 20 to 200 kilohertz (kHz), whereas human hearing normally tops out at around 20 kHz.
While using echolocation, the bats emit a series of short, high-frequency sounds from their mouths or nostrils that bounce off objects and surfaces and then return to the animals ears. Since high-frequency waves do not diffract, or bend, extensively, these ultrasonic vibrations provide bats with accurate maps of their surroundings. 

Multiple choice physics range of hearing sound: production of sound audible, infrasonic and ultrasonic sounds different sounds

Echocardiography is used to diagnose heart diseases which utilises infrasonic waves.

  1. True

  2. False

  3. Ambiguous

  4. Data insufficient
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

An echocardiogram (also called an echo) is a type of ultrasound test that uses high-pitched sound waves that are sent through a device called a transducer. The device picks up echoes of the sound waves as they bounce off the different parts of your heart. These echoes are turned into moving pictures of your heart that can be seen on a video screen.
Hence, the statement is false.

Multiple choice physics range of hearing sound: production of sound audible, infrasonic and ultrasonic sounds different sounds

Sound of frequency below $20 \ Hz$ is called

  1. audio sounds

  2. infrasonic

  3. ultrasonic

  4. supersonics
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Sound waves are categorized on the basis of their frequency range.

Sound of frequency below $20 \ Hz$ is called as infrasonic. Sound of frequency above $20 \ kHz$ is called as ultrasonic whereas sound of frequency in between $20 \ Hz$ to $20 \ kHz$ is called as audio sound.

Multiple choice physics energy production

Green house effect is the:

  1. trapping of radiation in the atmosphere

  2. trapping of water molecule in the atmosphere<div>
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  3. trapping of gases in the atmosphere

  4. none of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Our atmosphere allows the high frequency radiation (Infrared rays) to pass through it, which comes from sun. This radiation reaches to earth and after some absorption (this radiation is also absorbed and radiated by green house gases), earth reflects back low frequency radiation (Infrared rays) which cannot pass through the atmosphere. This radiation is trapped in our atmosphere and keeps our atmosphere warm, this is called green house effect.

Multiple choice physics energy production

Green house effect was discovered by: 

  1. Fischer

  2. Joseph Lister

  3. Joseph Fourier

  4. None
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Process of warming of planet's surface and its lower atmosphere by the absorption of infrared radiations of long wavelength given out from the surface of a planet is known as green house effect.  In 1824, Joseph Fourier discovered the green house effect.

Multiple choice physics energy production

Which of the following is not a greenhouse gas?

  1. Carbon dioxide

  2. Sulphur dioxide

  3. Methane

  4. Ozone
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Carbon dioxide, methane, and ozone are well-known greenhouse gases. Sulphur dioxide is primarily an air pollutant that causes acid rain, not a primary greenhouse gas.

Multiple choice physics energy production

Ozone layer blocks the radiations of wave length

  1. less than $3 \times 10^{-7}$ m

  2. equal to $3 \times 10^{-7}$ m

  3. more than $3 \times 10^{-7}$ m

  4. All of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The ozone layer absorbs harmful ultraviolet radiation, specifically UV-C and some UV-B, which have wavelengths shorter than approximately 300 nm (3 * 10^-7 m).

Multiple choice physics energy production

Carbon monoxide present in the air is the cause of acid rain.

  1. True

  2. False

  3. Ambiguous

  4. Data insufficient
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

false,
pollution from burning of fossil fuels is the major cause of acid rain. The main chemicals in air pollution that create acid rain are sulfur dioxide ($s{o} _{2}$) and nitrogen ($N{o} _{x}$).