Tag: comparison of speed of sound with speed of light

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

Sounds travels quickest in_____

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

  1. air

  2. water

  3. vaccum

  4. solids

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Correct Option: A

A worker lives at a distance of 1.32 km from the factory. If the speed of sound in air is 330 m$s^{-1}$, how long will the sound of factory siren take to reach the worker?

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

  1. 1 s

  2. 2 s

  3. 3 s

  4. 4 s

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Correct Option: D
Explanation:

Given,


Distance $=1.32\,km=1320\,m$

Speed of sound in air $=330\,m/s$

We have,

$Time=\frac{Distance}{Speed}$

$Time=\frac{1320}{330}=4\,s$

Thus it would take $4\,s$ for the sound of the factory siren to reach the 
worker.

A thunder tap is heared 5 second after the lightening flash. The distance of the flash is (velocity of sound in air is 345 m/sec.) :

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

  1. 3560 m

  2. 1725 m

  3. 1780 m

  4. 1815 m

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Correct Option: B
Explanation:

Given,

$v=345m/s$
$t=5sec$
The distance of the flash is,
$d=vt$
$d=345\times 5=1725m$
The correct option is B.

Two waves of wavelengths $\lambda$ and $(\lambda + \triangle \lambda)$ produce $6$ beats per second. If $\dfrac {\triangle \lambda}{\lambda} = \dfrac {\lambda + \triangle \lambda}{51}$, find the speed of sound wave in a gas in which these waves produce beats?

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

  1. $316\ m/s$

  2. $310\ m/s$

  3. $306\ m/s$

  4. $326\ m/s$

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Correct Option: D

Flash and thunder are produced simultaneously. But the thunder is heard a few seconds after the flash is seen. Why?

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

  1. The speed of sound is greater than the speed of light.

  2. The speed of sound is equal to the speed of light.

  3. The speed of light is greater than the speed of sound.

  4. The speed of light is less than the speed of sound.

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Correct Option: C
Explanation:

Flash and thunder are produced simultaneously. But the flash is seen first and then the sound is heard. This is because the speed of sound in air is very less than the speed of light in air.

Speed of sound in air $=334\,m/s$
Speed of light in air $=3\times 10^8\,m/s$

The speed of light in vaccum is....

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

  1. $3 \times {10^8}m/s$

  2. $0.3 \times {10^8}m/s$

  3. $9 \times {10^8}m/s$

  4. $30 \times {10^8}m/s$

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Correct Option: A

The time interval between a lightning flash and the first sound of thunder was found to be $5 \ s$. If the speed of sound in air is $330  \ ms^{-1}$, find the distance of flash from the observer.

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

  1. $1650 \ m$

  2. $165 \ m$

  3. $330 \ m$

  4. None of the above

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Correct Option: A
Explanation:

The speed of the sound, distance traveled and the time taken relationship is given as follows.


$Speed\; of\; sound=\dfrac { Distance\; travelled}{ Time\; taken} $

From this equation the Distance traveled is derived as 
$Distance\; travelled=Speed\; of\; sound\times Time\; taken$


That is, $Distance\; travelled=330\; m/s\times 5\; seconds$, given that the speed of sound is 330 m/s.

= 1650 meters.

Hence, the distance of flash from the observer is 1650 meters.

The speed of sound in a certain medium is $960 m/s$. If $3600$ waves pass over a certain point in 1 minute, the wavelength is,

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

  1. $2 m$

  2. $8 m$

  3. $4 m$

  4. $16 m$

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Correct Option: D

When a tuning fork of 500 Hz is used, the first and second resonating lengths of closed air column are found to be 18 cm and 54 cm respectively. Find the velocity of sound in S.I. system.

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

  1. $120{ms}^{-1}$

  2. $240{ms}^{-1}$

  3. $360{ms}^{-1}$

  4. $480{ms}^{-1}$

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Correct Option: C

An observer measures speed of light to be C when he is stationary with respect to the source. If the observer moves with velocity $\displaystyle v$ towards the source then the velocity of light observed will be :

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

  1. $\displaystyle c- v$

  2. $\displaystyle c + v$

  3. $\displaystyle \sqrt{1-v^2/c^2}$

  4. $\displaystyle c$

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Correct Option: D
Explanation:

Speed of light does not change with the frame of reference.  Option 'D' is correct.