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physics > waves > Flashcards

waves Flashcards

paper 1 - 4.1 to 4.17

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1
Q

what do waves transfer

A

energy not matter

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2
Q

what are transverse waves & examples (4)

A

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

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3
Q

what are longitudinal waves & examples (3)

A

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

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4
Q

parts of a transverse wave (3)

A

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

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5
Q

what is amplitude

A

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

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6
Q

parts of a longitudinal wave

A

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

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7
Q

what is a wave

A

an oscillation that transfers energy and info without matter

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8
Q

what is frequency

A

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

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9
Q

what is wavelength

A

distance between the same point on 2 adjacent waves

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10
Q

what is a period

A

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

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11
Q

what is wave velocity

A

speed and direction of a wave

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12
Q

what is a wavefront diagram

A

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

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13
Q

what is reflection

A

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

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14
Q

what is refraction

A

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

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15
Q

what is transmission

A

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

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16
Q

what is absorption

A

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

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17
Q

what is ultrasound

A

sound with a frequency above 20,000Hz

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18
Q

what is infrasound

A

sound with a frequency below 20Hz

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19
Q

what speed does sound travel at in air

A

340m/s

20
Q

what speed do EM waves travel at

A

3x10^8m/s

21
Q

equation using period and frequency

A

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

22
Q

wavespeed equation

A

v (m/s) = f(Hz) x λ(m)

23
Q

speed equation

A

s=d/t

24
Q

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

A

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

25
Q

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

A

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

26
Q

measuring speed of waves on water - practical (6)

A
  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
27
Q

wavespeed in a solid - practical (4)

A

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

28
Q

what objects absorb most

A

opaque

29
Q

what’s the angle of incidence

A

angle between incident ray and normal

30
Q

what’s the angle of reflection

A

angle between reflected ray and normal

31
Q

law of reflection

A

angle of incidence = angle of reflection

32
Q

what’s the angle of efraction

A

angle between refracted ray and normal

33
Q

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

A

angle of incidence > angle of refraction

34
Q

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

A

angle of incidence < angle of refraction

35
Q

why does light refract

A

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

36
Q

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

A

both decrease, frequency is the same

37
Q

how does sound travel (4)

A

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

38
Q

how do we hear (5)

A

-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

39
Q

human hearing range

A

20-20,000 Hz

40
Q

uses of ultrasound

A

-industrial
-medical imaging
-echo sounding

41
Q

how is ultrasound useful for industry

A

-find flaws in materials

42
Q

how is ultrasound used in medicine (3)

A

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

43
Q

how is ultrasound useful for echo sounding

A

-for sonar systems to find submarines, fish, shipwrecks

44
Q

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

A

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

45
Q

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

A

-transverse
-slower
-only travel through solid

physics (2 decks)

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