Summer review - Waves

Question 1

How sound is made

Answer 1

Vibrations

Question 2

Some sources of vibration

Answer 2

Vocal chords, speaker cone, violin strings

Question 3

What part of the ear vibrates

Answer 3

Ear drum

Question 4

How does sound travel from source to our ears

Answer 4

A connecting medium in the form of a longitudinal wave

Question 5

What is a longitudinal wave

Answer 5

A wave where the vibrations are parallel to the flow of the sound energy

Question 6

What happens to particles and air pressure when sound travels through air?

Answer 6

The air vibrates parallel to the source of flow of sound energy

Question 7

Describe an experiment showing sound travels as a longitudinal wave

Answer 7

A speaker is next to a candle and played

The air in front of it is caused to vibrate

The candle flickers left and right in time with the speakers vibration

Question 8

What is the bell jar experiment

Answer 8

A bell is placed inside a jar and rung

Air is removed making inside the jar a vacuum

The bell is no longer audible proving sound cannot travel through a vacuum

Question 9

What are the relative speeds in a vacuum, a gas, a liquid and a solid of sound

Answer 9

Vacuum = 0m/s

Gas = 330m/s

Liquid = 1450m/s

Solid = 4000m/s

Question 10

What is meant by ‘Mach 1’

Answer 10

Something travelling at Mach 1 is travelling at the speed of sound

Question 11

How do you measure the speed of sound

Answer 11

Speed = distance/time

Question 12

What happens when Mach 1 is exceeded

Answer 12

A sonic boom

Question 13

How to create an audible echo

Answer 13

Make a noise far enough a way from a smooth surface

Far enough so it doesn’t merge with the original song and smooth so it comes back directly at you

Question 14

How to measure the speed of sound using echoes

Answer 14

Make a sound, start timer, stop timer when echo is heard.

Speed = 2d/t

Question 15

Give uses of echoes

Answer 15

Echo-location (bats,dolphins)
Sonar
Lunar laser ranging

Question 16

What is the standard echo calculation

Answer 16

Speed = 2 x distance/time

Question 17

What is reverberation

Answer 17

The merged noise of the sound and the echo when the echo time is less then 0.1s

Question 18

What are the definitions of frequency and amplitude

Answer 18

Frequency - the number of vibrations per second

Amplitude - the maximum displacement of the vibrating medium from its equilibrium position

Question 19

How is frequency related to pitch

Answer 19

The higher the frequency the higher the pitch

Question 20

How is amplitude related to amplitude

Answer 20

The higher the amplitude the louder the sound

Question 21

What is the range of human hearing

Answer 21

20Hz to 20kHz

Question 22

How is Age related to the range of human hearing

Answer 22

The older you get the smaller your range of hearing

Question 23

How does noise-induced hearing loss affect ability to hear sounds

Answer 23

The worse your noise-induced hearing loss the worse your range of hearing

Question 24

How to interpret CRO wave forms

Answer 24

The height of the wave indicates the amplitude

The number of waves seen on the screen indicates the frequency

Question 25

How to minimise noise induced hearing loss

Answer 25

Limit time spent hearing overly loud noises, the louder the less time you can spend hearing it

Question 26

What is a compression and what is a rare fraction

Answer 26

Where air particles are bunched together there is a high pressure compression

Where they are spaced out there is a low pressure rarefaction