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AS Physics > Definitions 3 > Flashcards

Definitions 3 Flashcards

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1
Q

Progressive waves

A

Waves which transfer energy not matter as a result of oscillations or vibrations

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2
Q

Transverse waves

A

Waves where the oscillations of the particles in perpendicular to the direction of energy travel, resulting in crests and troughs

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3
Q

Longitudinal waves

A

Waves where the oscillations of the particles are parallel to the direction of energy travel

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4
Q

Frequency

A

The number of oscillations per unit time

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5
Q

Period

A

The time taken for one complete oscillation

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6
Q

Amplitude

A

The maximum distance of the particles in a wave, amplitude can never be negative

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7
Q

Displacement

A

The distance of a point on a wave from its rest or equilibrium position

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8
Q

Phase difference

A

The difference in the relative positions of two points on two waves of the same frequency

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9
Q

Intensity

A

The power per unit area or the energy passing through a unit area per unit time

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10
Q

Doppler effect

A

The change in observed frequency when a source moves relative to an observer

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11
Q

Electromagnetic waves

A

Transverse waves that can travel through a vacuum at the speed of light, they are formed from electric and magnetic fields oscillating at right angles

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12
Q

Polarisation

A

The restricting of the oscillations of the particles in a transverse wave to one direction at right angles to the direction of transfer of energy

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13
Q

Coherence

A

Two or more waves that have a constant phase difference and the same frequency, they do NOT need to have the same amplitude or wavelength

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14
Q

Principle of superposition

A

When two or more transverse or longitudinal waves travelling in opposite directions overlap to produce resultant displacements equal to the sum of the displacements on the original waves

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15
Q

Node

A

A position long a stationary wave with no vibration or zero amplitude

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16
Q

Antinode

A

A position along a stationary wave with maximum amplitude

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17
Q

Constructive interference

A

When two or more waves in phase produce a resultant wave with double the amplitude since the peaks and troughs of both waves line up, it is seen as bright fringes on a diffraction grating

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18
Q

Destructive interference

A

When two or more waves in anti-phase produce a wave with zero amplitude since the peaks on one of the waves lines up with the troughs of the other, it is seen as dark fringes on a diffraction grating

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19
Q

Stationary waves

A

Stationary waves are produced by the superposition of two waves of the same frequency and amplitude travelling in opposite directions

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20
Q

What are the properties of standing waves?

A
  1. The waves superposing must have the same frequency and amplitude
  2. They have nodes and antinodes
  3. All points between adjacent nodes vibrate in phase
  4. All points in adjacent loops oscillate in anti-phase
  5. The peaks and troughs of a standing wave do not move
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21
Q

Interference

A

Interference occurs whenever two or more waves superpose, it is the phenomenon when two coherent waves travel in opposite directions and overlap, leading to observable patterns of constructive and destructive interference

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22
Q

Diffraction

A

The spreading out of waves when they pass through or around an obstruction, any type of waves can be diffracted

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23
Q

Wavelength

A

The distance between points on successive oscillations of a wave that are in phase

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24
Q

What happens when the time-base on a CRO turns off?

A

A straight vertical line will show on the screen

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25
Q

Relationship between wavelength and frequency

A

Wavelength is inversely proportional frequency at a constant wave speed

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26
Q

What is intensity proportional to?

A

I ∝ amplitude^2 and frequency^2

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27
Q

What is intensity inversely proportional to?

A

I ∝ 1 / radius^2
The energy of a wave decreases rapidly with increasing distance

28
Q

How is frequency related to energy in the EM wavespectrum?

A

The higher the frequency the more energy of radiation of the EM wave

29
Q

λ of radio waves

A

> 1x10^-1 ms

30
Q

λ of microwaves

A

10^-1 to 10^-3

31
Q

λ of infrared waves

A

10^-3 to 7x10^-7

32
Q

λ of visible light

A

7x^-7 to 4x10^-7

33
Q

λ of UV

A

4x10^-7 to 10^-8

34
Q

λ of X-rays

A

10^-8 to 10^-10

35
Q

λ of gamma rays

A

10^-10 to 10^-16

36
Q

Why can’t longitudinal waves be polarised?

A

Since the particles of longitudinal waves oscillate parallel to the direction of travel

37
Q

What happens when unpolarised light falls on a polariser?

A

The intensity of unpolarised light will always fall by a half when it moves through a polariser

38
Q

What if the polariser and analyser have the same orientation?

A

The transmission axes of polariser and analyser are 0° to each other, meaning the intensity of the light entering the analyser from the polariser will always equal toe intensity of the transmitted light leaving the analyser

39
Q

What if the polariser and analyser are at right angles to each other?

A

The transmission axes are 90° to each other, meaning the intensity of light transmitted through the analyser will always be zero

40
Q

The equation for polarisation

A

I transmitted = I incident * cos^2(θ)

θ = the angle between the polarisation direction of the incoming light and the transmission axis of the polariser

41
Q

How do you calculate the length of a standing wave in a string?

A

L = nλ/2
n = 1,2,3…

42
Q

How do you calculate the length of a standing wave in a tube open at one end?

A

L = nλ/4
n = 1,3,5… odd only

43
Q

Why do standing waves in tubes with one end open have odd harmonics?

A

Since there is a node always formed at one end and an antinode at the open end, causing only odd multiples of 1/4λ to form

44
Q

How do you calculate the length of a standing wave open at both ends?

A

L = nλ/2
n = 1,2,3…

45
Q

What are the conditions for two source interference?

A
  1. The sources of the waves must be coherent monochromatic
  2. The slits must be narrow
46
Q

What happens to a wave when it is diffracted?

A

The amplitude is decreases, but all other properties remain the same

47
Q

Path difference

A

The difference in distance one wave has to travel compared to another to reach the same point

48
Q

How do you calculate the path difference for constructive interference?

A

nλ
n = the order of the maxima

49
Q

How do you calculate the path difference for deconstructive interference?

A

(n +1/2)λ
n = the order of the minima you want
To find the path difference find the difference between the two wavelengths

50
Q

Double slit interference equation

A

λ = ax/D
a = distance between slits
x = successive bright fringe width
D = distance between slits to screen

51
Q

Diffraction grating

A

A diffraction grating is a plate on which there is a very large number of parallel, identical, close-spaced slits; when coherent, monochromatic light is incident on a grating, a pattern of narrow bright fringes is produced on a screen

52
Q

Diffraction grating equation

A

dsin(θ) = nλ
d = spacing between adjacent slits
θ = angle to the central maxima
n = order of maxima

53
Q

How do you calculate the spacing between adjacent slits?

A

d = 1/N
N = lines per m,mm,cm…

54
Q

How do you calculate the highest order of maxima visible?

A

n = d/λ
since sin(90) = θ = 1
if n is a decimal value, round down to nearest integer

55
Q

How do you calculate the angle between maxima and central maxima?

A

θ = tan-1(h/D)

h = n * x (distance between successive maxima)
D = distance between slits to screen

56
Q

What do bright fringes look like?

A

They appear as bright bands of lights; they are evenly spaced and their intensity decreases from either side of the central bright fringe

57
Q

How do you find amplitude from CRO?

A

Amplitude = number of boxes that equal the amplitude * the time voltage setting

58
Q

How do you find the period from a CRO?

A

Period = the number of boxes from one peak to another * time base setting

59
Q

Time base setting

A

The time base refers to how many seconds each box is worth

60
Q

Compressions and rarefactions on a displacement distance graph

A

Compressions and rarefactions always appear at x = 0 on the graph

60
Q

How do you identify a compression?

A

Compression = if the displacements above and below the point at x = 0 are coming towards each other

61
Q

How do you identify a rarefaction?

A

Rarefaction = if the displacements above and below the point at x = 0 are heading away from each other

62
Q

What are the conditions for superposition?

A
  1. The waves must be the same type
  2. The waves must be coherent
  3. The amplitude does not necessarily need to be the same
63
Q

What is diffraction affected by?

A

The extend to which diffraction depends on the width of the gap compared to the wavelength of the waves

  1. When the gap is smaller, there is more diffraction
  2. When the wavelength of larger, there is more diffraction
  3. Diffraction is the most prominent when the width of the gap is equal to the wavelength
64
Q

Monochromatic light

A

Monochromatic light has a single-wavelength

65
Q

What happens to the bright and dark fringes when the intensity of the light is reduced?

A

Both the bright and dark fringes will become darker

AS Physics (3 decks)

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