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physics paper 2 > waves > Flashcards

waves Flashcards

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1
Q

progressive wave

A

wave which transfers energy from one place to another with a wave front which travels through the material

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2
Q

longitudinal wave

A

waves which the particles oscillate in the same direction as energy propagation

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3
Q

transverse waves and give examples

A

waves where the particle oscillations are perpendicular to the energy propagation i.e electromagnetic waves

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4
Q

frequency

A

number of waves passing through a point per second

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5
Q

wavelength

A

distance between two adjacent corresponding points on a wave

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6
Q

amplitude

A

max displacement of the wave from its equilibrium position

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7
Q

what is the phase difference of a wave and what is it measured in

A

the amount one wave lags behind another as a proportion of the wavelength. measured in radians or degrees

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8
Q

what do each of the ‘axes’ on an oscilloscope measure

A

vertical divisions = voltage/amplitude

horizontal divisions = time

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9
Q

refraction

A

when a wave bends at a boundary between two materials due to the difference in density causing it to speed up or slow down

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10
Q

true or false: a wave can either be refracted or reflected at a boundary, but never both

A

false: at low angle of incidence most will be refracted, but some will reflect

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11
Q

true or false: diffraction is most noticeable when the wavelength is much larger than the gap the wave is travelling through

A

false

the most diffraction is seen when the gap and the wavelength are the same size

if the wavelength is much bigger the waves will be mostly reflected

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12
Q

can all waves be polarised

A

no, only transverse waves

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13
Q

what is the difference between a polarised and unpolarised wave

A
  • polarised waves only contains waves oscillating along one axis
  • unpolarised waves can be oscillating in any direction perpendicular to the axis of propagation
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14
Q

describe how a ripple tank might be used to investigate diffraction

A
  • create water waves in the tank
  • vary the size of the gap for them to pass through
  • note how the direction of the waves passing through changes
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15
Q

polarised light is being passed through a rotating polarisation filter. what would happen to the intensity of the light passing through

A

it would vary from a maximum (all light passes through) when the axis of polarisation and the axis of the filter line up to a minimum (no light passes through) when the axes are perpendicular

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16
Q

how is intensity defined in terms of power

A

intensity is power / area

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17
Q

how are intensity and amplitude related

A

intensity is proportional to amplitude ^2

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18
Q

true / false: all electromagnetic waves have the same time period

A

false.

they all travel at the same speed - but their wavelengths, frequencies and time periods vary

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19
Q

how fast do electromagnetic waves travel in a vacuum

A

the speed of light

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20
Q

true or false: the magnetic field and electric field in a electromagnetic wave are parallel to each other

A

false: the electric and magnetic field are at right angles to each other

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21
Q

put the following in order from highest to lowest frequency
x-rays, radio, microwaves, uv, visible

A

highest
- x-rays
-UV
- visible
-microwaves
- radio
lowest

22
Q

which type of EM radiation has a wavelength of approximately 1 Pm

A

infra red is between 700 nm and 1mm

23
Q

what is the range of wavelengths commonly known as visible light

A

300 - 700 nm

24
Q

true/false: microwaves can be polarised using a metal grid rather than a polarising filter

A

true - this is because the wavelength of microwaves is sufficiently large than the grid works as a polarising filter

25
Q

what is meant by the refractive index of a material

A
  • measure of how fast light travels in a material compared to its speed in a vacuum

n = c/v

26
Q

a beam of light is shone at a boundary between air and glass. as the angle of incidence is increased from0 to 90 what would you see

A

at 0 all of the light would pass into the material along the normal

the light would then be seen to be refracted

eventually the light would bend so much it would start to be reflected back

27
Q

what is the name given to the angle of incidence at which light will reflect off a boundary rather than refracting in the medium

A

the critical angle

sinC = 1/n

28
Q

waves can ‘superpose’ - what does this mean

A

two waves in the same place will combine

29
Q

what is the name given to what happens to light at angles greater than the critical angle

A

total internal reflection

30
Q

what are the two types of interference

A

constructive and destructive

31
Q

describe an experiment to investigate the principle of superposition using sound

A
  • use two speakers, a moderate distance apart, connected to the same signal generator to transmit sound waves
  • walk along a line perpendicular to the speakers- you should hear alternating loud and quiet points
  • this is because in some places the waves from each speaker constructively interfere (loud) and in some places its destructive
32
Q

coherence

A

have the same frequency and wavelength and a fixed phase difference often 0 in exam questions

33
Q

if two waves are in phase will they constructively or destructively interfere

A

constructively

34
Q

true/false: path difference and phase difference are two names for the same thing

A

false

path difference is the difference in distance that two waves have travelled in terms of the wavelength

phase difference is the difference in the point in the cycle of two waves as a proportion of a full wave cycle

35
Q

why is a laser useful in showing interference and diffraction

A

it produces monochromatic light

36
Q

what is Youngs double slit experiment

A

a single source of light directed towards a double slit which creates two coherent beams of light. this interferes as it hits the screen and creates an interference pattern

37
Q

describe the interference pattern created using white light

A

the interference pattern would be a repeating coloured spectrum along the screen, with a bright white point directly in front of the slit

38
Q

increasing the slit width increases the width of the central diffraction maximum true or false

A

true

39
Q

what equation relates the wavelength of light to the slit spacing and distance to the screen

A

lambda = ax/D

a = slit spacing
x = fringe spacing
D = distance to screen

40
Q

which two properties of light can only be explained if it is a wave

A
  • diffraction
  • interference
41
Q

when shining light through a diffraction grating there is a maximum number of fringes which would be produced. how would you find this maximum number

A

Nlambda = Dsintheta

rearrange fro n using theta = 90

42
Q

what is a stationary wave

A

consist of alternating fixed pattern of nodes (points with zero amplitude) and antinodes (points with maximum amplitude) no energy is transferred across the wave

43
Q

node

A

a point with no vibrations in which the resultant amplitude is 0

44
Q

antinode

A

a point with maximum vibration in which the resultant amplitude is at maximum

45
Q

what are the conditions for a stationary wave to be produced

A
  • the waves must be coherent
  • they must be travelling in opposite directions

these conditions are often met when a wave is reflected onto itself

46
Q

give an example of an experiment you could do to show a stationary wave

A
  • use an oscillator to pass a wave along a string which is fixed at one end
  • the stationary wave will from when the progressive wave is reflected off the fixed end
46
Q

give a similarity and a difference between stationary waves and progressive waves

A

similarity: both have wavelength, frequency, amplitude

difference: stationary waves don’t transmit energy from one place to another

47
Q

how could you use the formation of stationary waves in a resonance tube to find the speed of sound

A
  • create a closed end pipe using a hollow pipe inside a measuring cylinder contains water
  • use a tuning fork producing a known frequency and hold it above the tube
  • move the tube up until you find the first position which causes resonance
  • this length will be a quarter of the wavelength
  • use speed = frequency x wavelength
48
Q

harmonics

A

harmonics are points where the stationary wave form doesn’t change because the waves one act direction are reinforcing each other

49
Q

a stationary wave on a string is made to oscillate at its fundamental frequency (1st harmonic) - how many nodes and antinodes would you see

A

nodes - 2
antinodes - 1

physics paper 2 (8 decks)

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