CB Chapter 6 Waves and sounds

Question 1

What is a wave?

Answer 1

Oscillations or vibrations about a rest position. The oscillations have a direction whilst the wave itself also has a direction.

Question 2

What do waves transfer and what do they not transfer?

Answer 2

Waves transfer energy across locations but do not transfer matter

Question 3

What are the main types of waves?

Answer 3

Transverse waves and longitudinal waves

Question 4

What are oscillations in waves?

Answer 4

The to-and-fro movement of parts of the medium (EG: a slinky’s coils moving back-and-forth)

Question 5

What is a transverse wave?

Answer 5

A wave where the oscillations are at rights angles to the direction of travel (EG: a slinky’s coils moving up and down whilst the wave moves to the right)

Question 6

What are two important features of a longitudinal wave?

Answer 6

Compressions and rarefactions

Question 7

What is a longitudinal wave?

Answer 7

A wave where the oscillations are in the same direction as the direction of travel (EG: a slinky’s coils being compressed and stretched out as the wave moves to the right)

Question 8

What is a compression?

Answer 8

A section where the medium is more compressed (EG: part of a slinky’s coils being compressed together due to a longitudinal wave)

Question 9

What is a rarefaction?

Answer 9

A section where the medium is more stretched out (EG: part of a slinky’s coils being stretched out due to a longitudinal wave)

Question 10

What are examples of transverse waves?

Answer 10

electromagnetic waves: radio waves, microwaves, infrared, light, ultraviolet, X-rays, gamma rays

Question 11

What is an example of a longitudinal wave?

Answer 11

sound waves

Question 12

Are seismic waves transverse or longitudinal?

Answer 12

P (primary) waves, able to travel massive distances through the Earth, are longitudinal. S (secondary) waves, which are slower, are transverse

Question 13

What happens when you speak?

Answer 13

compressions and rarefactions travel through the air

Question 14

What is the speed of a wave?

Answer 14

The speed at which the wave moves. Its SI unit is m/s

Question 15

What is the frequency of a wave?

Answer 15

The number of waves passing any point per second. Its SI unit is hertz (Hz). 1 Hz = 1 oscillation / second

Question 16

What is the period of a wave?

Answer 16

The time needed for one full oscillation. Its SI unit is seconds (s).

Question 17

What equation links period and frequency?

Answer 17

period (s) = 1/frequency (Hz)

Question 18

What is the wavelength?

Answer 18

The distance between any point on a wave and its equivalent point on the next wave. Its SI unit is metres (m)

Question 19

What is the amplitude?

Answer 19

The maximum distance a point moves from its rest position when a wave passes. Its SI unit is metres(m)

Question 20

What is the wave equation?

Answer 20

speed (m/s) = frequency (Hz) * wavelength (m)

Question 21

What is the wave equation in symbols?

(Imagine this in your mind and remember the symbols)

Answer 21

v = fλ

λ is the Greek letter lambda

Question 22

Why does the wave equation work?

Answer 22

EG: assume λ = 2 m. There is a flag, and after 1 second, 3 waves have passed the flag. The frequency is 3 Hz. The waves have moved 3 wavelengths in 1 second. 3 Hz (frequency) * 2 m (wavelength) = 6 m/s (speed)

Question 23

What is a ripple tank?

Answer 23

A transparent, shallow tray of water with a light shining downwards through it onto a screen below. The ripples are preferably produced by a motor

See an image

Question 24

What is reflection?

Answer 24

Reflection is when waves hit a surface and travel in a new direction away from the surface

Question 25

How does reflection occur?

Answer 25

The waves are reflected from the surface at the same angle they hit it

Question 26

What can happen when waves slow down, what is this called?

Answer 26

The waves can change direction. This is called refraction

Question 27

What is diffraction?

Answer 27

The process of waves bending around the sides of obstacles and spreading out as they pass through gaps

Question 28

When is diffraction significant?

Answer 28

When the size of a gap is about the same as the wavelength

Question 29

How does a wider gap affect diffraction?

Answer 29

A wider gap produces less diffraction

Question 30

What are some real-world examples of reflection?

Answer 30

Light reflects from mirrors and sound reflects from hard surfaces

Question 31

What are some real-world examples of refraction?

Answer 31

Light bends when it passes from air into glass or water

Question 32

What is a reason you can hear sound around corners?

Answer 32

Due to diffraction, sound bends around obstacles like walls and buildings

Question 33

What suggests light waves have very short wavelengths?

Answer 33

Light spreads when it passes through tiny holes and slits. Due to diffraction, this suggests light waves have very short wavelengths

Question 34

What suggests radio waves have long wavelengths?

Answer 34

Some radio signals can bend around large obstacles like hills. Due to diffraction, this suggests radio waves have very long wavelengths

Question 35

How do you hear sound (simple)?

Answer 35

Sound waves reach your ear and make your ear-drums vibrate, making you hear a sound

Question 36

What causes sound waves?

Answer 36

Vibrations

Question 36

What are some objects which produce sound waves through vibrations?

Answer 36

Guitars (vibrating strings), trumpets (vibrating air inside) and tuning forks (vibrating prongs)

Question 36

How does air pressure vary in compressions and rarefactions?

Answer 36

Air pressure is higher than average in compressions and lower than average in rarefactions