waves

Question 1

what do waves transfer

Answer 1

energy not matter

Question 2

what are transverse waves & examples (4)

Answer 2

-oscillations are perpendicular to direction of travel
-water, light, EM, S waves

Question 3

what are longitudinal waves & examples (3)

Answer 3

-oscillations are parallel to direction of travel
-P waves, sound, (ultrasound)

Question 4

parts of a transverse wave (3)

Answer 4

-highest point = peak
-lowest = trough
-distance between 2 peaks = wavelength

Question 5

what is amplitude

Answer 5

the maximum displacement of a point on wave measured from undisturbed position

Question 6

parts of a longitudinal wave

Answer 6

-high pressure area=compression
-low pressure=rarefaction
-distance between 2 compressions = wavelength

Question 7

what is a wave

Answer 7

an oscillation that transfers energy and info without matter

Question 8

what is frequency

Answer 8

no. of complete waves passing a certain point per second, number of waves produced by a source per second

Question 9

what is wavelength

Answer 9

distance between the same point on 2 adjacent waves

Question 10

what is a period

Answer 10

time taken for 1 full cycle of a wave to be completed

Question 11

what is wave velocity

Answer 11

speed and direction of a wave

Question 12

what is a wavefront diagram

Answer 12

representation of a wave made up of a series of wavefronts. these are lines drawn through identical points on a wave

Question 13

what is reflection

Answer 13

when a wave bounces back as it meets a boundary between 2 materials

Question 14

what is refraction

Answer 14

when a wave changes direction as it passes across the boundary between 2 materials at an angle to the normal

Question 15

what is transmission

Answer 15

when a wave passes across a boundary from 1 material into another and continues travelling

Question 16

what is absorption

Answer 16

when a wave transfers energy to the energy store of a material

Question 17

what is ultrasound

Answer 17

sound with a frequency above 20,000Hz

Question 18

what is infrasound

Answer 18

sound with a frequency below 20Hz

Question 19

what speed does sound travel at in air

Answer 19

340m/s

Question 20

what speed do EM waves travel at

Answer 20

3x10^8m/s

Question 21

equation using period and frequency

Answer 21

time period (s) = 1/frequency (Hz)

Question 22

wavespeed equation

Answer 22

v (m/s) = f(Hz) x λ(m)

Question 23

speed equation

Answer 23

s=d/t

Question 24

how to measure speed of sound in air - practical with oscilloscope(8)

Answer 24

1.connect 2 microphones to an oscilloscope
2.set up a speaker & a signal generator to produce a sound wave with a specific frequency
3.place microscopes equidistant to speaker
4.set up oscilloscope so it shows sound waves detected at each microphone. in the initial set up the 2 traces should line up
5.slowly move 1 microphone away from speaker. the trace from this speaker will shift sideways on oscillosope
6.keep moving the microphone away until the traces line up again this is 1 wavelength away
7. measure distance
8. use v=fλ to find speed

Question 25

measuring speed of sound in air - practical with wall (6)

Answer 25

1.stand 100m from a wall clap and wait for echo 2.distance travelled is 2x distance from u to wall 3.measure distance stand beside person who's going to clap 4.start clock when clap and stop when hear echo 5.repeat 10x and calculate av. time 6. use s=d/t

Question 26

measuring speed of waves on water - practical (6)

Answer 26

1. set up ripple tank with about 5cm depth of water 2.adjust height of wooden rod so it just touches the surface of water 3.switch on light & motor & adjust frequency until low frequency waves can be seen clearly 4.measure length of waves then divide by no. of waves to record wavelength. camera can help 5.count no. of waves passing a point in 10s. f=no.waves/10 6.calculate wavespeed

Question 27

wavespeed in a solid - practical (4)

Answer 27

1.suspend a metal rod horizontally using clamp stands and rubber bands 2.hit 1 end of rod with hammer. hold a phone with f app 3.measure length of rod. wavelength will be twice length of rod 4.v=λf

Question 28

what objects absorb most

Answer 28

opaque

Question 29

what's the angle of incidence

Answer 29

angle between incident ray and normal

Question 30

what's the angle of reflection

Answer 30

angle between reflected ray and normal

Question 31

law of reflection

Answer 31

angle of incidence = angle of reflection

Question 32

what's the angle of efraction

Answer 32

angle between refracted ray and normal

Question 33

when a light ray goes from a less dense to a more dense medium how are the refracted rays change

Answer 33

angle of incidence > angle of refraction

Question 34

when a light ray goes from a more dense to a less dense medium how are the refracted rays change

Answer 34

angle of incidence < angle of refraction

Question 35

why does light refract

Answer 35

a change in speed when it enters the optically denser material. light is slower in water/glass so when it enters at angle it changes direction

Question 36

what happens to the wavelength & speed when a light ray enters an optically denser medium

Answer 36

both decrease, frequency is the same

Question 37

how does sound travel (4)

Answer 37

-speaker vibrates -vibrates surrounding particles -oscillations are passed from particle to particle -vibrations pass to ear

Question 38

how do we hear (5)

Answer 38

-sound passes through the pinna to ear canal -compressions & rarefactions in air move drum -ossicles vibrate and pass them through semi-circular canals -cochlea converts vibrations to electrical signals -auditory nerve passes signals to brain

Question 39

human hearing range

Answer 39

20-20,000 Hz

Question 40

uses of ultrasound

Answer 40

-industrial -medical imaging -echo sounding

Question 41

how is ultrasound useful for industry

Answer 41

-find flaws in materials

Question 42

how is ultrasound used in medicine (3)

Answer 42

-probe emits ultrasound which partially reflects at boundary between tissue -time taken for echoes to return is used to build image -prenatal/foetal scans

Question 43

how is ultrasound useful for echo sounding

Answer 43

-for sonar systems to find submarines, fish, shipwrecks

Question 44

P-waves: -type -relative speed -can travel through outer liquid core?

Answer 44

-longitudinal -fastest -can travel through liquid & solids but at diff. speeds

Question 45

S-waves: -type -relative speed -can travel through outer liquid core?

Answer 45

-transverse -slower -only travel through solid