Speed of Sound vs Speed of Light

Q.

Flash of lightning reaches us earlier than the sound of thunder. Explain the reason.

Q. A cricket ball is seen to hit the bat first and the sound of hitting is heard a little later. Why?

Q.

What is light?

Q.

One of the prongs of a tuning fork is struck against a rigid wall. A to and fro motion of the prongs is observed. Then, the vibrating fork is touched to a still water surface.

Which of the following phenomena is observed in the water?

1. Water surface starts vibrating

2. Water boils

3. Water freezes

4. Water body starts rotating

Q.

Explain why, the flash of a gun shot reaches us before the sound of the gun shot.

Q.

A strong sound signal is sent from a ship towards the bottom of the sea. It is received back after $1second$. What Is the depth of the sea? (Speed of sound in water= $1450m/s$)

Q.

What happens inside optical fiber?

1. Diffraction

2. Polarization

3. Interference

4. Total internal reflection

Q. We see lightning before thunder, as the speed of light is more than the speed of sound in air.

1. False
2. True

Q. Do mechanical waves lose energy as they travel through a medium? Why?

Q.

Sound is a:

1. form of energy

2. disturbance

3. wave

4. all of these

Q.

The speed of light in air is :

(a) $3\times {10}^{8}m{s}^{-1}$

(b) $330m{s}^{-1}$

(c) $5100m{s}^{-1}$

(d) $3\times {10}^{10}m{s}^{-1}$

Q.

Sounds are produced by _______ objects.

Q. What is meant by sound intensity?

Q. Sound waves travels _________ than light in vacuum.

1. faster
2. slower
3. not slower
4. Can't travel

Q.

Which of the following are true about sound wave

1. 1

2. Travels fastest in gases

3. Laws of reflection is not valid

4. Particles oscillate about their mean position

Q. A thunder is heard 4 seconds after the lighting. At what distance, the lightning occured?

1. 1480 m
2. 1380 m
3. 2380 m
4. 1000 m

Q.

Sound waves are:

1. Mechanical waves.

2. Non-mechanical waves.

3. Zero-energy waves.

4. Electromagnetic waves.

Q. 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.) :

1. 3560 m
2. 1725 m
3. 1780 m
4. 1815 m

Q. why do fan make sound when slows down?

Q.

State any three differences between light waves and sound waves?

Q. Question 2
Why are sound waves called mechanical waves?

Q. A man fires a gun at a distance of $150\text{m}$ from a cliff. A second man who is standing $300\text{m}$ away from the first man hears the gunshot $1\text{s}$ after he sees the flash. When will the second man hear the echo from the cliff? (Take the speed of sound as $300\text{m/s}$.)

1. $2\text{s}$ after seeing the flash
2. $2\text{s}$ after hearing the gunshot
3. $1\text{s}$ after seeing the flash
4. $4\text{s}$ after hearing the gunshot

Q. The moon is at a distance of $4\times {10}^{8}m$ from the earth. A radar signal is transmitted from the earth will reach the moon in about

1. $2.6s$
2. $1.3s$
3. $5.2s$
4. $6.5s$

Q. A sound made on the surface of a lake takes $3s$ to reach a boatman. How much time will it take to reach a diver inside the water at the same depth?
Velocity of sound in air $=330m{s}^{-1}$.
Velocity of sound in water $=1450m{s}^{-1}$.

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

1. True
2. False

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

Q. (a) What is the speed of $\gamma -rays$ ?
(b) Are they deflected by an electrostatic field ? [2 MARKS]

Q. We can see the flash of lightening from clouds much before we hear the thunder. This is because

1. sound travels faster than light
2. sound travels much slower than light
3. sound has same velocity as light
4. none of the above

Q. Lightning and thunder take place in sky and at the same distance from us. Explain why lightning is seen earlier and thunder is heard later ?

Q.

Assertion (A)– The speed of sound in hot region is greater than that in cold region.
Reason (R)– As the temperature increases the molecules have more energy and thus disturbance is transmitted slowly.

1. A is false while R is true

2. Both A and R are true, and R is the correct explanation of A

3. A is true while R is false

4. Both A and R are true, but R is not the correct explanation of A.