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OCR PHYSICS A > MODULE 4: WAVES AND QUANTUM > Flashcards

MODULE 4: WAVES AND QUANTUM Flashcards

(73 cards)

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1
Q

What is a progressive wave

A

Oscillation through space that transfers energy

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2
Q

Types of waves

A

Transverse

Longitudinal

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3
Q

Transverse vs longitudinal

A

Oscillation is perpendicular to energy transfer in transverse, parallel in longitudinal

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4
Q

Examples mechanical waves

A

Sound water etc

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5
Q

Examples transverse

A

EM, surface water ripples

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6
Q

What is the wave equation

A

v = lambda * f

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7
Q

Types of wave graphics and axis

A 
Displacement distance (y,x)
Displacement time (y, x)
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8
Q

What is phase difference

A

Difference between how far in a single oscillation two waves are at a point in time, in radians

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9
Q

How to find distance between two points on wave of phase different x

A

(x/2pi) * wavelength or (x/360) etc for degrees

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10
Q

What is reflection

A

When a wave bounces off a surface, staying in the same medium.
Angle of incidence is always the angle of reflection

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11
Q

What is refraction

A

When a wave changes medium, eg air to water

or deep to shallow water in terms of surface ripples

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12
Q

What is constant in refraction and what changed

A

Frequency is const

So speed and wavelength change

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13
Q

What is diffraction

A

Spreading of a wave when is goes through a aperture (gap)

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14
Q

When is diffraction significant and when not

A

When aperture size is close to wavelength

When it’s much much smaller very little happens

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15
Q

What is wave polarisation

A

When a waves oscillations move to only one plane, making it plane polarised

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16
Q

What parts make up the EM wave

A

Magnetic field , and electric field both in different planes with phase different of 90 deg

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17
Q

What is polarisation filter

A

A piece of ‘paper’ which when two are oriented correctly block all light, because it’s all plane polarised

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18
Q

Which em wave has lowest wavelength, and which has highest wavelength

A

Radio have highest

Gamma have lowest

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19
Q

Name em spectrum

A

Radio micro infrared visible ultraviolet (X-ray gamma)

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20
Q

What is intensity of a progressive wave

A

Radiant power passing at right angle per unit surface area (it hitting the area)

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21
Q

Intensity equation and unite

A

I=P/A Wm^-2

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22
Q

What two things is intensity proportional to

A

1/r^2 of a surface area

amplitude^2 of a wave

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23
Q

4 properties of EM waves

A

transverse
Travel in vacuum
Speed of 3*10^8ms^-1
Have two components electric and magnetic fields

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24
Q

What are polarisation filters called

A

Polaroid paper

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25
How to test polarisation with microwaves/visible light waves
EQUIP: microwave transmitter and receiver, metal grille (or two pieces of polariod paper if it’d visible light) EXPERIMENT: rotate the grille or paper to see how the receiver doesn’t receive as much anymore
26
What is refraction index
Ratio of light speed to the speed of the light in the medium. Not between 0 and 1 n=c/v
27
Refractive index of air
1.0003
28
What is the refraction law
n1 sin theta 1 = n2 sin theta 2
29
What is total internal reflection and what are the two properties
When the light wave reflects back into the same medium 1. destination material has lower refractive index 2. Angle of incidence I > critical angle
30
What happens when angle of incidence is equal to the critical angle
Light refracts along the boundary the media
31
What two things happen when the angle of incidence is less than the critical angle
``` Refraction Partial reflection (the light REFLECTS but not as intense) ```
32
What is the critical angle
minimum angle which rays of light passing through a denser to less dense medium are able to be totally reflected. (TIR)
33
When can you use critical angle and what is the equation
when light going from material to air sin critical angle.(C) = 1/n N = refractive index
34
Where does critical angle equation come from
If angle of incidence is equal to critical angle light travels along the boundary, so theta 2 is 90 because it’s 90 from the normal. Sin90 = 1 so n1sin1 = 1, because it’s material to air and air refractive index is 1 So sinC = 1/n
35
Refractive index can be throughout of as
How much slower the speed of light in the medium is compared to air (where n is 1)
36
What is a photon
Packet of energy, a quantum of electromagnetic energy
37
How the energy of a photon related to the frequency of the wave
E=hf, Planck constant
38
What is the electron volt
A unit of energy for dealing with small amounts of energy
39
Electron volt symbol and unit
eV = charge * voltage, voltage = energy / charge, so eV v energy in joules
40
What happens when a LED looses energy
Emits photons
41
What is the photoelectric effect
When electromagnetic radiation is used to remove electrons from the surface of metals
42
How to test to find planks const
have multiple coloured LEDs adjust voltage until light just appears to come through Record V and the wavelength of the LED eV = approx hf = hc/lambda Plot threshold V against 1/lambda, so the gradient is hc/e. C and e are known constants, so you can find out planks constant from that
43
What is used to test photoelectric effect
Gold leaf electroscope | With negative zinc plate shining electrons onto it from laser etc, gold leaf will move up
44
What is the work function and threshold frequency
Work function is minimum energy of a metal to free an electron from its surface Threshold frequency is the minimum frequency of the incoming wave to free electrons from the surface
45
Work function formula
hf (energy) = Ek(max) + Φ
46
What is Einstein’s equation
The work function equation hf = ekmax + Φ
47
Two quantum rules
Photon can interact with only one electron at a time | Energy is conserved in photon electron interaction
48
What is a work function for a given element
Energy needed to free an electron from an electron shell
49
What graph is used to determine h as the gradient
ekmax = hf - Φ y = Mx + c c = -Φ, so Φ is -c m is h is frequency and ekmax are plotted
50
What is wave particle duality
Electromagnetic waves have a dual nature, they travel as waves but act like photons Act according to wave and photon model
51
What is de Broglies equation and what does it mean
wavelength = h / p, where p is momentum so lambda = h/mv | a particle travelling through space with momentum p has an associated wavelength
52
How to test de broglie equation
Electron diffraction tube: Accelerated electrons pass through sheet of graphite The atomic structure of graphite is layered sheets of electrons, the separation is similar to the de Broglie wavelength of the electrons causing them to diffract The diffracted electrons create rings on the screen in front of the graphite sheet, showing the diffracted electrons
53
What is superposition
When to waves meet and combine
54
Principle of superposition
When waves meet, resultant displacement is the sum of displacements of the waves
55
What is coherent waves
Constant phase difference and frequency, therefore wavelength and speed and same type
56
What is interference
Superposition of waves from two coherent sources
57
What is path difference
Distance (multiples of wavelengths) between two coherent wave sources
58
What is constructive interference
When the waves have a phase difference of 0 or 2pi | The resultant wave is double the amplitude
59
What is destructive interference
When waves phase difference is pi, 180. Waves displacements cancel out Resultant wave is practically no amplitude
60
What path differences given constructive and destructive waves
Constructive have any integer multiply of lambda eg 1lambda, 10lambda Destructive have any integer and a half wave, eg 1.5, 2.5, 0.5, n/2 lambda
61
What is Young’s double slit
Experiment which uses two narrow slits to determine the wavelength of monochromatic light
62
What is monochromatic light
Light with only one wavelength, not a combination light white light
63
Young double slit formula
``` Wavelength = ax/D X = fringe sep a = slit sep D = screen to slit sep ```
64
Describe experiment to determine young double slit wavelength of laser
EQUIP: laser, paper with two small slits, piece of cardboard EXPERIMENT: shine the laser at the slits so they diffract, and observe the diffraction pattern on the cardboard which is placed distance D away, measure the slit separation a. Measure some amount of red dots per side of the middle central maximum. Count the dots and take one away from that to measure the empty spaces. Divide the measurement by this number to get the fringe separation Calculate wavelength
65
What is a stationary wave
When two progressive waves superpose when travelling in opposite directions.
66
What does a stationary wave move like
It doesn’t move only it’s amplitude appears to move, it’s amplitude moves getting bigger and smaller but it appears to not move, it’s distance looks always 0 https://en.wikipedia.org/wiki/Standing_wave See animation
67
What is an anti node and a node
Node is point with no amplitude | Antinode has maximum amplitude
68
Differences between progressive and stationary waves
Progressive waves transfer energy | Phase difference in stationary waves is between 0 and pi only
69
Average wavelength of radio micro andinfrared
1000,10^-2,10^-5
70
Average wavelength of visible light
10^-6
71
Average wavelength of UV
10^-8
72
Average wavelength of X-ray and gamma
X-ray 10^-10 | Gamma 10^-12
73
How can the time constant be measured for a capacitor circuit (3)
Connect voltmeter across resistor in parallel with capacitor (1) use a stopwatch to record when it gets to 37 percent of its initial value (e to the minus 1) (1) this is the time constant , time to reach 37 percent of its initial value

OCR PHYSICS A (5 decks)

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