Sound

Question 1

What type of wave is sound?

Answer 1

A longitudinal wave

Question 2

What is the audible frequency of sound?

Answer 2

20Hz to 20000Hz

Question 3

Speed of sound in solids, liquids and gases

Answer 3

Solids: 3000m/s
Liquids: 1500m/s
Gases: 330m/s

Question 4

Experiment to show that sound cannot travel in a vacuum. (diagram)

Answer 4

1) When we switch it on, the electric bell, the hammer vibrates and a sound is heard.
2) When the vacuum pump switched, the intensity of the sound will decrease until no sound is heard because a vacuum has been created inside the jar.

Question 5

What is the distance between two consecutive compressions known as?

Answer 5

Wavelength

Question 6

Experiment to determine speed of sound in air (5)

Answer 6

1) By using a measuring tape, person A and B stand a known distance apart in an open field
2) Person A shoots the pistol in the air
3) On seeing the flash, observer B starts his stopwatch and then stops it on hearing the sound.
4) The time interval is recorded
5) Speed = distance÷time

Question 7

Precautions for the experiment to determine the speed of sound in air (2)

Answer 7

1) Distance should not be less than 500m
2) Experiment should be carried out in an open field to avoid echo

Question 8

Define echo

Answer 8

An echo is a sound reflected from a hard surface. For an echo to be heard, the sound must travel twice the distance between the source and the hard surface.

Question 9

Describe how an ultrasound works

Answer 9

The incident ultrasound is reflected by various layers of tissues and bones in the body. The reflected sound waves are picked up by the receiver and the information is analysed by a computer to produce a picture

Question 10

Experiment to determine the speed of sound in air using echo (5)

Answer 10

1) Person A makes a sharp clapping sound by knocking two blocks of wood together
2) He repeats the clapping each time he hears an echo
3) Person B starts his stopwatch and counts the number of claps starting from 0 and stops the stopwatch after 20 claps
4) The time to hear one echo is calculated (t÷20)
5) speed of sound = distance covered by 1 echo÷time to hear 1 echo

Question 11

How to determine the depth of the sea (

Answer 11

1) An ultrasonic sound is emitted by the ship towards the sea bed
2) On hitting the sea bed, the ultrasound is reflected and picked up by the receiver of the ship.
3) The time taken to travel twice the depth of the sea is measured by the CRO
4) Depth= speed x (time on CRO÷2)

Question 12

How is loudness related to amplitude?

Answer 12

Loudness is proportional to amplitude

Question 13

How is pitch related to frequency and time period?

Answer 13

Pitch is proportional to frequency. Pitch is inversely proportional to time period