Sound

Q.

Sound becomes hazardous noise pollution at decibels

1. above $120db$

2. above $80db$

3. above $50db$

4. above $30db$

Q.

A stone dropped from the top of a tower of height 300 m splashes into a pond of water at its base. When will the sound of the splash be heard at the top?
(Velocity of sound = $340m{s}^{-1}$ and g = 9.8 $m{s}^{-2}$)

1. 5.6s

2. 8.7s

3. 5.4s

4. 6.7s

Q. Question 2
Describe with the help of a diagram, how compressions and rarefactions are produced in air near a source of sound.

Q.

How does the sound produced by a vibrating object in a medium reach your ear?

Q.

Sound which is pleasant to ears is called___.

Q. Explain, the reason sound propagates faster through metals even though they are denser than gases is that they are stiffer ( i.e., less incompressible). for example: steel is 6000 times denser than air but 2000000 times more elastic than yeah, so sound travel 16 times faster in steel then in air.

Q.

The sound wave is a sequence of __ and rarefactions.

Q. Through which medium sound travels faster, iron or water? Give reason.

Q.

Sound having loudness above 80dB is called ___

Q.

The speed of sound depends on the properties of the medium through which it travels.

1. True

2. False

Q.

Sound cannot be propagated through____________________

Q.

A longitudinal wave travels in the form of alternate compressions and rarefactions.

1. True
2. False

Q.

A sound wave has different speeds in different mediums because:

1. more incompressible the medium is, faster the speed

2. more compressible the medium is, faster the speed

3. more the density, slower the speed

4. lesser the volume, faster the speed

Q. Cite an experiment to show that sound needs a material medium for its propogation.

Q.

Consider the following statements:
Statement 1: No sound can be heard on the surface of the moon.
Statement 2: Temperature of the surface of the Moon is very high and hence sound waves cannot be produced.
Choose the correct options.

1. perpendicular direction

2. same direction

3. either A or B

4. neither A or B

Q. Wat disadvantages would be there if we hd just one ear instead of two

Q.

What do you understand by the term longitudinal wave? Give two examples.

Q.

Choose the correct option

1. Sound cannot travel in vacuum

2. Sound is a mechanical wave and propagates as an oscillation of particles through the medium. So they cannot travel in vacuum.

Q.

The velocity of sound is maximum in which medium?

Q. How temperature affect speed of sound?

Q.

A sound wave is a sequence of __ and rarefactions.

Q.

When sound waves travel from a rarer medium to a denser medium, its speed:

1. decreases

2. remain constant

3. increases

4. may increase or decrease

Q.

Sound waves have different speeds in different media because:

1. more compressible the medium is, faster the speed

2. more incompressible the medium is, faster the speed

3. more the density, slower the speed

4. lesser the volume, faster the speed

Q.

The sound waves in air are

1. Seismic waves

2. Transverse waves

3. Longitudinal waves

4. Partially longitudinal and partially transverse

Q.

Differentiate between music and noise.

Q.

Which of the following are properties of a sound wave?

1. Obeys laws of reflection

2. is a mechanical wave

3. is a longitudnal wave

4. All of these

Q. We have two ears because:
i) It helps our brain to sense that from which direction sound is coming.
ii) If there is hearing loss in one ear one can still hear from another.

1. Both statements are true.
2. Both statements are false.
3. Statement (i) is only true.
4. Statement (ii) is only true.

Q.

When sound waves travel from a rarer medium to a denser medium with same elastic properties, its speed:

1. decreases

2. remain constant

3. increases

4. may increase or decrease

Q. Explain how does the sound produced by a vibrating object in a medium reach our ears? [3 marks]

Q. We have two ears because:
i) It helps our brain to sense the direction of incoming sounds.
ii) In the case of hearing loss in one ear, one can still hear from another.

1. Both statements are false.
2. Statement (i) is only true.
3. Statement (ii) is only true.
4. Both statements are true.