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Physics A Level > 5 Waves > Flashcards

5 Waves Flashcards

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1
Q

Amplitude

A

The max displacement of a particle from the midpoint of the oscillation (m)

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2
Q

Time period

A

The time taken to complete one oscillation (s)

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3
Q

Frequency

A

The number of oscillations per second (Hz)

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4
Q

Wave speed

A

The distance travelled by the wave each second (m/s)

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5
Q

Wavelength

A

The distance between consecutive points at which oscillations are in phase

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6
Q

Equation linking frequency and time period (learn)

A

f= 1/T

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7
Q

Equation velocity frequency and wavelength

A

V=f x wavelength

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8
Q

Longitudinal waves

A

When particles oscillate in the same direction as the wave travel

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9
Q

Transverse waves

A

When particles oscillate perpendicular to the wave direction

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10
Q

Wavelength of gamma rays

A

10^-16 to 10^-11

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11
Q

Wavelength of x-rays

A

10^-14 to 10^-10

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12
Q

Wavelength of ultra violet

A

10^-10 to 10^-8

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13
Q

Wavelength of visible light

A

4x10^-7 to 7x10^-7

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14
Q

Wavelength of infrared

A

10^-7 to 10^-3

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15
Q

Wavelength of microwaves

A

10^-4 to 10^-1

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16
Q

Wavelength of radio

A

10^-3 to 10^5

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17
Q

Properties of gamma rays

A

Destroying tumours

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18
Q

Properties of x rays

A

See bones

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19
Q

Properties of ultraviolet

A

Checking banknotes

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20
Q

properties of Visible light

A

Photosynthesis and to see

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21
Q

Properties of infrared

A

Night vision

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22
Q

Properties of microwaves

A

Mobile phones and satellite communications

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23
Q

Properties of radio

A

Many signals can be transmitted

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24
Q

Equation of intensity power and area

A

I= P/A

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25
Q

Constructive superposition

A

When two waves are in phase and make a larger waves

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26
Q

Destructive superposition

A

When two waves are completely out of phase and cancel out

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27
Q

When are waves coherent

A
  • same type
  • same frequency
  • constant phase difference
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28
Q

Path difference

A

The difference between the distances from two sources to a given point

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29
Q

When is an interference pattern observed?

A
  • they are two coherent sources

* they have a similar amplitude

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30
Q

Standing waves

A

When two waves of equal frequency and amplitude are travelling at the same speed in opposite directions superimpose

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31
Q

At antinodes what is the path difference

A

Zero path difference so max amplitude

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32
Q

At nodes what is the path difference?

A

Half a wavelength pi/2 therefore there is min amplitude

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33
Q

Characteristics of progressive waves

A
  • energy is transferred in direction of wave travel
  • all points on wave have some amplitude
  • adjacent points in wave have a different phase relationship
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34
Q

Characteristics of standing waves

A
  • energy is stored in each vibrating particle
  • amplitude varies
  • all points between consecutive nodes have a constant phase relationship
35
Q

Equation for velocity in standing wave in string

A

V^2= T/U

V= velocity
T=tension
U= mass per unit length

36
Q

Equation for frequency in standing wave in string (learn)

A

f =1/wavelength x route(T/U)

37
Q

Refractive index

A

The ratio of the change in speed from medium 1 to medium 2

38
Q

Snells law (learn)

A

n= sin(I)/sin(r)

39
Q

Critical angle

A

When the angle of incidence has an angle of refraction of 90° (travels along the boundary)

40
Q

Equation for critical angle

A

SinC = n2/n1

SinC = 1/n1

41
Q

Uses for total internal reflection

A

Binoculars and fibre optic cables

42
Q

Converging lens

A

Where the light rays refract and meet at a focal point

43
Q

Diverging lens

A

Where the light rats refract away from each other

44
Q

Where is the focal point with a diverging lens

A

There is a virtual focal point in front of the lens

45
Q

Focal length

A

The distance from the centre of the lens to the focal point

46
Q

Equation for power of a lens

A

Power = 1/focal length

47
Q

What happens to the power of lenses when they are combined

A

Pt= P1 + P2 + P3

48
Q

The lens equation

A

1/f = 1/u + 1/v

f = focal length
u= distance of ray before lens 
v= distance of ray after lens
49
Q

Equation for magnification

A

Magnification = height of image/ height of object

50
Q

What happens if you get a negative focal length

A

It’s a virtual image

51
Q

What is plane polarisation

A

When two sheets of Polaroid can be roared at 90° to each other to block out light

52
Q

Diffraction

A

The spreading of waves after they have passed through an aperture

53
Q

When is diffraction greatest

A

When the wavelength is the same as the width of the gap

54
Q

How is the multiple slit diffraction grating pattern observed

A

The maxima appear where the small coherent waves have superimposed constructively to produce sharply defined lines

55
Q

Equation for diffraction grating

A

n x wavelength = d x sin(x)

n= order if maximum
d= slit separation
x= angle between central max and diffracted max
56
Q

How can the max number of orders be found

A

n

57
Q

Laws of reflection

A
  • angle of incidence= angle of reflection

* the incident ray, reflected ray and the normal all lie in the same plane

58
Q

Pulse echo technique

A

When a wave is reflected off a material and the time recorded to work out how far away the material is (used in ultrasound)

59
Q

What properties do photons exhibit?

A

Wave and particle properties

60
Q

Equation showing energy given by each photon

A

E = hf

h= Plancks constant
f= frequency
61
Q

Photoelectric effect

A

The emission of electrons from a material when light is shone into its surface

62
Q

Work function

A

The minimum amount of energy that electrons need in order to be released from a metal

63
Q

Einstein’s photoelectric equation

A

hf= I + KE

h= Plancks constant
f= frequency 
I= work function
KE= kinetic energy
64
Q

Threshold frequency

A

The minimum frequency required to reach the work function

65
Q

How can the kinetic energy of photoelectric be found?

A

By measuring their stopping potential

66
Q

Equation for stopping potential

A

eVs= 1/2mv^2

67
Q

What is the most stable orbit in an emission spectrum

A

The ground state

68
Q

Permitted orbitals

A

Levels on the emission spectrum where the electron is in an excited state

69
Q

Equation linking momentum and wavelength

A

Wavelength = h/p

h= Plancks constant
p= momentum
70
Q

How does decreasing the intensity of the incident light on a metal have an affect on the photoelectric effect.

A
  • lower intensity would contain less photons
  • less photons absorbed by electrons
  • less electrons emitted
71
Q

Ground state of an atom

A

Lowest energy state of an electron in an atom

72
Q

Why are only certain wavelengths of light emitted due to the photoelectric effect?

A
  • electrons gain energy and move up energy levels
  • they then fall down energy levels
  • the energy change is given out in the form of a photon
  • the energy levels are discrete
  • the energy of the photon is equal to the change in energy level
  • there are only a limited amount of energy differences and only a corresponding set of frequencies/wavelengths
73
Q

Explain how the fact that electrons have a range of KE up to a specific max is evidence of the particle nature of light.

A
  • particle nature of light has one photon to one electron
  • E=hf so energy transfer is limited
  • KE=hf-work function does there is a max KE
  • if there were waves the energy would build up over time so there would be no max KE
74
Q

Photon

A

A discrete package of electromagnetic light energy

75
Q

What is an energy level

A

A discrete quantity of energy for an electron in the atom

76
Q

Why is the KE in the photoelectric equation KEmax

A

Because some energy may be transferred to the metal rather than the electron

77
Q

Why, in an electron gun, is the cathode connected to the negative terminal?

A

Electrons are repelled by the cathode and attracted to the anode

78
Q

Explain how polarisation can block out light.

A
  • unpolarised light includes oscillations in all directions
  • when plane polarised the oscillations of light are in a single plane
  • which is perpendicular to direction of energy transfer
  • when the second filter is parallel the light is transmitted so can still be seen
  • when the second filter is perpendicular the plane polarised light is absorbed so no light is seen
79
Q

When using pulse echo technique, why are pulses used rather than a continuous beam?

A

So they can tell which received pulse matches which sent pulse

80
Q

What is an inverted image?

A

When the image produced it upside down

81
Q

What is virtual image

A

When the image is perceived to be produced on the same side of the lense as the object

82
Q

What equation is used for image height object height and focal length of a real image

A

1/f= 1/u +1/v

83
Q

What equation is used for image height object height and focal length of a virtual image

A

1/f= 1/u -1/v

84
Q

What does u, v and f stand for in the equation 1/f= 1/u +1/v

A 
U= object height
V= image height
F= focal length

Physics A Level (11 decks)

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