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a level physics > waves > Flashcards

waves Flashcards

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1
Q

what do waves do

A

transfer energy without transferring matter

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2
Q

what is a progressive wave

A

a wave which carries energy from one place to another

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3
Q

how can you make a wave

A

having a particle or a field oscillate

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4
Q
A
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4
Q

what happens to the source of a wave as the wave moves

A

the source of the wave loses energy as the wave transfers the energy

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5
Q

how can you tell a wave carries energy?

A

things heat up, ionisation occurs, you can hear sounds

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6
Q

what is refraction

A

when a wave changes speed and direction as it moves from one medium into a different medium

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7
Q

what is reflection

A

when a wave bounces back

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8
Q

what causes the change in direction during refraction

A

as the speed of the wave slows down when it hits another medium at an angle.wave hits the medium at an angle one part of the wave slows down first before the other parts of the wave

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9
Q

what is diffraction

A

when a wave spread out as it passes through a gap or round an obstacle

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10
Q

what is displacement and what is it measured in

A

how far along a wave has moved from an undisturbed position. measured in metres,m. Displacement is usually the y - axis on a graph

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11
Q

What is amplitude

A

the maximum possible displacement of a wave. measured in metres

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12
Q

what is the crest

A

amplitude name for positive displacement

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13
Q

what is the trough

A

amplitude name for negative displacement

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14
Q

What is wavelength and what is it measured in

A

The distance of one whole wave cycle/oscillation. Measured in metres

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15
Q

what is a period of a wave and what is it measured in

A

The time taken for one whole wave cycle. measured in seconds

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16
Q

What is frequency and what is it measured in

A

The number of one whole wave cycle in 1 seconds. measured in hertz

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17
Q

what is phase

A

A measurement of a wave at one particular point

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18
Q

what is the phase difference

A

The amount by which one wave lags behind the other

Have to be on the same graph
At the same point of the waves e.g 2 crests

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19
Q

How do you calculate frequency? (period)

A

f = 1/period

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20
Q

what is the symbol for wavelength

A

lambda

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21
Q

What are the 2 ways to measure the parts of a wave cycle (not in metres)

A

degrees and radians (as in pi = 3.1415926535)

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22
Q

Give me 1/4 , 1/2, 3/4 and 1 wave cycle in degrees

A

1/4 = 90 degrees
1/2 = 180 degrees
3/4 = 270 degrees
1 = 360 degrees

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23
Q

give me 1/4, 1/2, 3/4 and 1 wave cycle in radians

A

1/4 = pi/2
1/2 = pi
3/4 = 1.5 pi or 3 pi/2
1 = 2 pi

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24
Q

What is phase difference measured in

A

degrees

25
Q

Whta happens if you have 2 waves with different amplitudes but the same frequencyin terms of phase difference

A

You get a phase difference of 0 degrees as amplitude doesnt matter when calculating phase difference

26
Q

What is a transverse wave

A

A wave which has oscillations perpendicular to the energy propagation (transfer) of the wave

27
Q

Are em waves transverse waves

A

yes all of them are

28
Q

What are em waves

A

they are vibrating electric and magnetic fields

29
Q

What are some examples of transverse waves

A
  • em waves
  • ripples in water
  • earthquake shock waves (S-waves)
30
Q

What is a longitudinal wave

A

A wave where the oscillation is parallel or along the energy propagation

31
Q

What are examples of a longitudinal wave

A

sound and earthquake shock waves (P-waves)

32
Q

What are the 2 main parts of a sound wave

A

rarefactions and compressions of the medium

33
Q

what is a rarefaction

A

when the matter along a sound wave is spaced out

34
Q

what is a compression in a sound wave

A

the bit of the wave when the matter is compressed

35
Q

What is a polarised wave

A

a wave that only oscillates in one direction

36
Q

what does a polarising filter do

A

it only transmits vibrations in one direction

37
Q

What is light (in terms of wave vibrations)

A

a mixture of waves that have different directions of vibrations

38
Q

what happens if you have two polarising filters at right angles

A

then no light will get through

39
Q

Why does 2 polarising filters at right angles not let light through

A

theres a lot to explain which wont fit in the card so heres a video that explains it: https://www.youtube.com/watch?v=JWy0QsBZgbk&list=PLlDtVvefFYT9NxoJ70Ns7Htg9Um2gUPRP&index=9

40
Q

What happens if 2 polarsing waves arent at right angles

A

The intensity of the wave will just be reduced

41
Q

Can polarisation happen for all waves

A

no, only for transverse waves

42
Q

What are some applications of polarised light

A

glare reduction, TV and radio signals

43
Q

What evidence proves the nature of transverse waves

A

light was discovered to be slightly polarised by reflection in 1808. Light was thought of as a longitudinal wave back then so it confused the scientists but in 1817 a scientist suggested light was a transverse wave made up of magnetic and electrical field which oscillate perpendicular to the direction of energy propagation which explains why light can be polarised

44
Q

How does glare reduction work

A

Light reflected of objects light water or tarmac or glass is partially polarised which can enter your eyes to cause glare. With a polarising filter at the right angle you can block out some of the light reducing the light intensity while still allowing some light through.

45
Q

How does TV and radio signals work with polarised waves

A

TV and other aerial signals are partially polarised cause of the orientation of the transmitting rod. This means to get a strong signal you have to align the receiving and transmitting rods together to get the strongest signal.

46
Q

What is antiphase

A

When the phase differences is exactly 180 degrees

47
Q

What is a stationary wave

A

A wave caused by 2 progressive waves with the same frequency and amplitude moving in opposing directions superposing; causing no energy to be transferred

48
Q

What is destructive superposition

A

When there is a phase difference of 180 degrees causing a wave to be formed which has the amplitudes subtracted

49
Q

what is constructive superposition

A

when there’s a phase difference of 0 degrees causing a wave to be formed where the amplitudes are added

50
Q

How can you demonstrate a stationary wave

A

a piece of string with an oscillator on one end and an object which can reflect the wave on the other end.

51
Q

What is resonant frequency

A

The amount of waves it takes for the wave produced by an oscillator to be reflected in time for another wave to be produced. Then the original and reflected wave will interfere constructively at antinodes and destructively at nodes. link: https://www.youtube.com/watch?v=pBHxnf7k7PU

52
Q

what is a node

A

point on a wave where the amplitude is 0m

53
Q

what is an antinode

A

The crest on a wave (the points of maximum amplitude

54
Q

what interference happens at nodes

A

destructive interference

55
Q

what interference happens at antinodes

A

constructive interference

56
Q

When is a stationary wave formed at resonant frequency

hint: wavelengths

A

When an exact number of half wavelengths fit on a string

57
Q

what are the harmonic and how many nodes and antinodes do they each have

A

harmonics are how many half wavelengths there are. e.g 3rd harmonic= 3 half wavelengths
nodes per harmonic = harmonic +number 1 e.g 3rd harmonic = 3 + 1 = 4 nodes
antinodes = harmonic number e.g 3rd harmonic = 3 anitnodes 1st harmonic = 1 antinode

58
Q

How do you setup for a stationary microwave

A

by having a microwave transmitter emit microwaves at a metal plate which reflect the plate. The nodes and antinodes can be detected by having a probe connected to a loudspeaker

59
Q

how do you setup for a stationary soundwave

A

loudspeaker connected to a tube of glass with air and powder.

60
Q

How can u calculate the speed of sound in a stationary soundwave

A

the powder in the glass are the nodes which are half of the wavelength so you can measure that distance and double it to get the distance of 1 full wave cycle

61
Q

What is the equation for the frequency of any harmonic

A

f = (1/2L)(square root of (T/mu))
L = length of string
T = tension of the string
mu = mass per unit length

a level physics (4 decks)

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