Questions
Flash and thunder are produced simultaneously. But thunder is heard a few seconds after the flash is seen. This is because:
- speed ofsound is greater than speed oflight
- speed of sound is equal to the speed of light
- speed of light is much greater than the speed of sound
- none of these
Correct comparison between light waves and sound waves is:
- Both are mechanical waves
- Both need a material medium for propagation
- Both can travel through vacuum
- None
Sound waves travels _________ than light in vacuum.
- faster
- slower
- not slower
- Can't travel
Sound waves travels _____ light in air
- faster than
- slower than
- at same speed as
- either faster than or with same speed as
The distance between tow adjacent particles which are in the same phase in a progressive wave is 20 cm. determine the velocity of the wave if its frequency is 10 Hz.
- $2 {ms}^{-1}$
- $40 {ms}^{-1}$
- $8 {ms}^{-1}$
- $80 {ms}^{-1}$
Light and Sound waves
- both are mechanical waves
- both need material media for propagation
- both can travel through vacuum
- are two different types of waves
The thunder of a cloud is heard later compared to flash of lightning because :
- speed of sound is greater than speed of light
- speed of light is greater than speed of sound
- speed of sound is the same as speed of light
- sound is obscured by the rain
You see lightning before you hear the thunder because
- Lightning is much brighter than thunder.
- Thunder is heavier than lightning.
- Light can travel through air but sound cannot.
- Sound travels slower than light.
Speed of sound wave in a gas is $v _{1}$ and tins speed of molecules of the gas at the same temperature is $v _{2}$. Then :
- $ v _{1} = v _{2}$
- $ v _{1} < v _{2}$
- $ v _{1} > v _{2}$
- $v _{1}\le\ v _{2}$
A source of frequency 500Hz emits waves of wavelength 0.2m.How long does it take to travel 300 m?
- 70 s
- 60 s
- 12 s
- 3 s.
Sounds travels quickest in_____
- air
- water
- vaccum
- solids
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?
- 1 s
- 2 s
- 3 s
- 4 s
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.) :
- 3560 m
- 1725 m
- 1780 m
- 1815 m
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?
- $316\ m/s$
- $310\ m/s$
- $306\ m/s$
- $326\ m/s$
Flash and thunder are produced simultaneously. But the thunder is heard a few seconds after the flash is seen. Why?
- The speed of sound is greater than the speed of light.
- The speed of sound is equal to the speed of light.
- The speed of light is greater than the speed of sound.
- The speed of light is less than the speed of sound.
The speed of light in vaccum is....
- $3 \times {10^8}m/s$
- $0.3 \times {10^8}m/s$
- $9 \times {10^8}m/s$
- $30 \times {10^8}m/s$
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.
- $1650 \ m$
- $165 \ m$
- $330 \ m$
- None of the above
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,
- $2 m$
- $8 m$
- $4 m$
- $16 m$
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.
- $120{ms}^{-1}$
- $240{ms}^{-1}$
- $360{ms}^{-1}$
- $480{ms}^{-1}$
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 :
- $\displaystyle c- v$
- $\displaystyle c + v$
- $\displaystyle \sqrt{1-v^2/c^2}$
- $\displaystyle c$
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.
- $390 {ms}^{-1}$
- $160 {ms}^{-1}$
- $330 {ms}^{-1}$
- $150 {ms}^{-1}$
A wave has a frequency of $5$ GHz.
What is the period of the wave?
- $200$ ps
- $0.2$ ns
- $20$ ns
- $20000$ $\mu s$
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?
- $h e^{-2} \mu^{-1} G^0$
- $h^2 e G^0 \mu$
- $h^0 e^2 G^{-1} \mu$
- $h G e^{-2} \mu^{0}$