Tag: comparison of speed of sound with speed of light

Questions Related to comparison of speed of sound with speed of light

The frequency of fundamental mode of vibration of an air column enclosed in a closed end pipe is 250 Hz. If its length is 33 cm, then find the velocity of sound in air.

physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

  1. $390 {ms}^{-1}$

  2. $160 {ms}^{-1}$

  3. $330 {ms}^{-1}$

  4. $150 {ms}^{-1}$

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Correct Option: C

A wave has a frequency of $5$ GHz.
What is the period of the wave?

physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

  1. $200$ ps

  2. $0.2$ ns

  3. $20$ ns

  4. $20000$ $\mu s$

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Correct Option: B
Explanation:

Given that,


Frequency $f=5 GHz=5\times10^{9}\ Hz$


The period of the wave is reciprocal of frequency.

$T=\dfrac{1}{f}$

$T=\dfrac{1}{5\times10^{9}}$

$T=2\times10^{-10}$

$T=0.2\ ns$

The period of the wave is $0.2\ ns$

Hence, B is correct option.

Which of the following product of $e, h, \mu, G$ (where $\mu$ is the permeability) be taken so that the dimensions of the product are same as that of the speed of light?

physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

  1. $h e^{-2} \mu^{-1} G^0$

  2. $h^2 e G^0 \mu$

  3. $h^0 e^2 G^{-1} \mu$

  4. $h G e^{-2} \mu^{0}$

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Correct Option: A

The ratio of speed of ultrasonic wave and sound wave is:

physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

  1. $=1$

  2. $>1$

  3. $<1$

  4. $>1$

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Correct Option: A
Explanation:

Ultrasonic wave is  defined as “inaudible sound with high frequency for human” the frequency of which generally exceeds 20 kHz. These days, sound wave which is not intended to be heard is also called Ultrasonic wave .


Ultrasonic wave is also a type of sound wave so ratio of velocity is $=1$

As the train crosses a stationary observer, the apparent change in frequency of sound in the ratio $5:3$. If the velocity of sound in air $332\ m/s$, then velocity of train is

physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

  1. $81\ m/s$

  2. $83\ m/s$

  3. $90\ m/s$

  4. $87\ m/s$

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Correct Option: A

A laser signal sent towards the moon returns after T seconds.If c is the speed of light, then  the distance of the moon from the observer is given by

physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

  1. cT

  2. $c{T^{ - 2}}$

  3. $\frac{{ct}}{2}$

  4. 2 cT

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Correct Option: C

The speed of sound is $330 ms^{-1}$ and that of light is $3\times 10^8 ms^{-1}$. The ratio of speed of sound to that of light is approximately $1 : 10^6$.

physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

  1. True

  2. False

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Correct Option: A
Explanation:

Speed Of Sound$(V)$  is,  $330m/s$  and  that of Light$(U)$  is,  $300*10^{6}m/s$

Now we have to find,  $V:U$  and i.e.,  $V:U=330:300*10^{6}\cong1:10^{6}$ , because in comparison to $U$(Speed of Light)  ,  Speed of Sound$(V)$  is comparetively very $small$.
So, we can assume that, Speed of Sound$(V)$  is $300m/s$  in comparison to that of Speed of Light$(U)$ that is  $3*10^{6}$
Hence,  $V:U=1:10^{6}$

Hence, it is True.
Option A is correct

If you hear a gun shot 1 seconds after it is fired, how far away from the gun are you? (speed of sound in air $=330 ms^{-1})$

physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

  1. 230 m

  2. 330 m

  3. 430 m

  4. 530 m

Show answer
Correct Option: B
Explanation:

Here we use the concept of Distance formula i.e.,  $d=vt$ , where  $d$  is the distance travelled,  $v$  is the speed and $t$  is the time taken.

Now, According to question;
Given;  $t=1s$  and  $v=330m/s$,
have to find  $d$  and that is,  $d=vt=330*1=330m$

Hence, option  B  is correct.

Light .......... travel in vacuum , but the sound ........ travel in vacuum.

physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

  1. Cannot , can

  2. Can, cannot

  3. Sometimes, never

  4. Never, sometimes

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Correct Option: B
Explanation:

The light can travel in vacuum, but the sound can not travel in vacuum. speed of light in air is $\displaystyle 3\times { 10 }^{ 8 }{ m }/{ s }$

Speed of light in air is about ....... times greater than the speed of sound in air.

physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

  1. Million

  2. Trillion

  3. Billion

  4. None

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Correct Option: A
Explanation:

The speed of light in air is $\displaystyle 3\times { 10 }^{ 8 }{ m }/{ s }$ which is about a million times greater than the speed of sound in air (i.e. 330 m/s at $\displaystyle { 0 }^{ \circ  }C$