p12 - wave properties

Question 1

how is sound caused?

Answer 1

mechanical vibrations in substance

Question 2

how can we test if sound can travel through a vacuum?

Answer 2

listening to a ringing bell in a ‘bell jar’
- ringing sound fades away as air is pumped out of a jar

Question 3

define longitude waves

Answer 3

direction of vibrations is parallel to direction of which the wave travels

Question 4

how is an echo produced?

Answer 4

when sound waves are reflected from hard, flat surfaces, such as walls, to produce an echo

Question 5

define transverse waves

Answer 5

direction of vibrations is perpendicular to direction in which waves travel

Question 6

define amplitude of a wave

Answer 6

height of the wave crest from midpoint of wave

Question 7

the greater the amplitude of wave…

Answer 7

the more energy it carries

Question 8

define wavelength

Answer 8

distance from one crest to next crest

Question 9

define wave frequency

Answer 9

number of wave crests passing a point in 1 second

Question 10

give unit of frequency

Answer 10

hertz, Hz

Question 11

define period of wave

Answer 11

time it takes for one wavelength to pass a point

Question 12

give equation for period of a wave

Answer 12

period of wave = 1/frequency

Question 13

give equation for wave speed

Answer 13

wave speed (m/s) = frequency (Hz) x wavelength (m)

Question 14

what do waves transfer?

Answer 14

energy and information, not matter

Question 15

how do you know direction the wave transfers energy?

Answer 15

same direction in which wave travels

Question 16

what is a longitudinal wave made up of?

Answer 16

• compressions
• rarefactions

Question 17

define mechanical waves

Answer 17

travel through a medium, e.g waves on springs and sound waves
- can be either longitudinal or transverse

Question 18

define electromagnetic waves

Answer 18

can travel through a vacuum, e.g light and radiowaves
- all transverse waves

Question 19

define incident waves

Answer 19

waves travelling towards a barrier or a boundary

Question 20

what happens when a barrier is placed in a ripple tank?

Answer 20

reflection takes place at barrier
- reflected wavefront moves away from barrier at same angle to the barrier as incident wavefront
- no change in speed or wavelength

Question 21

what happens when waves cross a boundary between differenct substances?

Answer 21

waves change speed and wavelength
waves may be:
- fully or partially reflected
- transmitted through substance
- absorbed by substance

Question 22

define refraction

Answer 22

• unless the waves meet the boundary at right angles, change in speed causes a change in direction