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AS Content remake Flashcards

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1
Q

What is the photoelectric effect?

A

When a certain frequency of light is shone onto different types of metals, the photons individually interact with the electrons in the metal causing them to gain enough energy to be released from the metal.

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2
Q

What is threshold frequency?

A

The minimum required frequency needed to be shone onto a metal for it to start emitting electrons.

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3
Q

What is the ’work function’?

A

The required energy needed to release an electron from a metal.

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4
Q

How does the work function change with the reactivity of a metal?

A

Generally, more reactive metals have a lower work function.

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5
Q

What is the equation for photon energy in photoelectric emission?

A

Photon energy = work function + kinetic energy of electron

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6
Q

What is stopping voltage?

A

The voltage necessary in a potential divider circuit to make the photocurrent zero

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7
Q

What is Plancks constant? (Value)

A

6.63x10^-34m

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8
Q

What is de broglie’s wavelength function?

A

Lambda = h (Planck constant) / p (momentum)

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9
Q

What is the equation for momentum? (Derived from the electron gun experiment)

A

P = sqrt( 2 x Ek x m )

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10
Q

What is the relation between wavelength and kinetic energy?

A

Lambda (wavelength) ∝ 1 / sqrt(Ek)

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11
Q

Def a photon

A

A photon is a quantum of EM radiation (like in cs with processes getting a quantum of runtime)

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12
Q

What is the equation for the energy of a photon?

A

E = (h (Planck constant) x c) / lambda (wavelength)
Or E= hc/lambda

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13
Q

What is the equation for the electron volt?

A

eV = (1/2)mv^2 where e is the elementary charge and V is voltage but v is velocity and m is mass

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14
Q

What is the name for an electron that has been released from a metal due to the photoelectric effect?

A

Photoelectrons

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15
Q

What two pieces of evidence show that light is a wave?

A

Light produces interference patterns and can also be diffracted which are only explained by light being a wave and following superposition.

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16
Q

What was de broglies suggestion about electrons behaving like waves?

A

If ’wave-like’ light showed particle properties, then ’particles’ such as electrons should be expected to show wave light properties

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17
Q

What experiment proved de broglie right about electrons behaving like waves?

A

The electron diffraction experiment

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18
Q

The equation for current in terms of charge including units

A

I = Q(coulombs) / T(seconds)

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19
Q

What is the value of the elementary charge e?

A

e = 1.6x10^-19 C

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20
Q

What two things could cause an increase in rate of charge flow?

A

More electrons passing through a given point (greater cross sectional area)
The same number of electrons electrons moving faster through the wire

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21
Q

What is Kirchhoff’s first law?

A

The sum of the currents into a junction is equal to the sum of the currents leaving the junction

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22
Q

How are materials classified by conductivity?

A

Their number density (number of free electrons per cubic meter)

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23
Q

What are the three categories of conductivity of material?

A

Insulators, semiconductors, conductors

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24
Q

What is the equation for current in terms of mean drift velocity?

A

I = Anev where A is cross sectional area in meters squared and v is velocity in ms

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25
Q

How does reducing the cross sectional area of a wire affect the drift velocity if flow of charge remains constant?

A

The drift velocity increases in the smaller area to compensate

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26
Q

What is Kirchhoff’s second law?

A

The sum of the e.m.f.s is equal to the sum of the p.d.s in a closed loop

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27
Q

What can Kirchhoff’s second law be broken down to? (Interpreted as)

A

The total energy transferred to the charges in a circuit is always equal to the total energy transferred from the charges as they move around the circuit.

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28
Q

How is current affected by components in a series circuit?

A

It isn’t, it is the same all the way round

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29
Q

What is the sum of the p.d. Across components in a circuit equal to?

A

The e.m.f. (Components with more resistance get a higher share of the voltage)

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30
Q

In a parallel circuit, how much of the current will a branch with twice the resistance of another branch receive?

A

Half of the current

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31
Q

How does Kirchhoff’s second law work in parallel circuits?

A

The sum of the e.m.f. Is equal to the sum of the p.d. of all the components in that closed loop (branch of the parallel circuit)

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32
Q

What does a power source need in order to output a high current?

A

A low internal resistance, such as a car battery

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33
Q

How is energy ‘lost’ in the cell of an electrical circuit?

A

Energy is ‘lost’ to heat as work has to be done by the charge carriers in the power source, for a chemical source, this is due to reactions between chemicals.

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34
Q

What is terminal p.d.?

A

The p.d. measured at the terminals of a power source

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35
Q

How does terminal p.d. differ from e.m.f.?

A

The terminal p.d. Is lower than the actual e.m.f. due to energy lost from internal resistance, these are called lost volts.

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36
Q

What is the equation for e.m.f. in terms of terminal p.d.?

A

Electromotive force = terminal p.d. + lost volts

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37
Q

How does an increase in current affect terminal p.d. and lost volts when the emf remains constant?

A

And increase in current means more charge carriers doing work in the cell which increases lost volts and decreasing terminal p.d.

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38
Q

What is the equation for lost volts?

A

V (Lost volts) = I (current) x r (internal resistance)

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39
Q

What’s the equation for emf from a power source (derived from e = v + lost volts)

A

emf = V (terminal p.d.) + I (current) x r (internal resistance) or emf = I (current) x (R (resistance) + r (internal resistance))

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40
Q

What is Kirchhoff’s second law?

A

The sum of the e.m.f.s is equal to the sum of the p.d.s in a closed loop

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41
Q

What is the equation for potential difference in terms of charge?

A

V = W(energy transferred) / Q(charge)

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42
Q

What property would an ideal voltmeter have in order to function most efficiently?

A

It would have infinite resistance so when connected, no current would actually pass through

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43
Q

Define voltage in terms of work done by the charge carriers

A

Voltage is work done by the charge carriers, thus, the charge carriers are losing energy as they pass through components

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44
Q

Def electromotive force? (e.m.f.)

A

e.m.f. Is when work is done on the charge carriers, essentially the charge carriers gain energy as they travel through a component such as a cell, battery or power pack

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45
Q

What is a second equation for the electromotive force?

A

E (e.m.f.) = W (energy transferred) / Q (charge)

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46
Q

What is the name of the process when electrons gain enough energy to escape the surface of a metal?

A

Thermionic emission - the emission of electrons through the action of heat

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47
Q

How does an electron gun work?

A

A heated filament is placed in a vacuum and a high p.d. Is applied between the filament and an anode, the filament then acts as a cathode and the freed electrons accelerate towards the anode gaining kinetic energy as they go. The electrons then go through a small hole in the anode creating a beam of electrons with a specific kinetic energy

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48
Q

What is the equation for calculating the work done on a single electron travelling from the cathode to the anode in the electron gun experiment? (Hint, not kinetic energy)

A

W (work done) = e x v (accelerating p.d.)

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49
Q

What is the equation for the work done on an electron to increase its kinetic energy?

A

eV (work done on an electron) = 1/2 x m (mass) x v^2 (velocity)

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50
Q

What assumption is being made when calculating the work done on an electron to increase it’s kinetic energy (in the electron gun experiment)

A

The electrons have negligible kinetic energy at the cathode (initial energy is almost 0)

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51
Q

How does increasing the accelerating p.d. In the electron gun experiment affect the velocity of the electrons?

A

It increases the kinetic energy (more energy being transferred to the electrons) so they have a greater velocity.

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52
Q

What is the equation for resistance?

A

R (resistance) = p.d. (Voltage) / Current
V = IR

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53
Q

What is the definition of an ohm?

A

The resistance of a component when a p.d. of 1 is produced per amp of current

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54
Q

What is Ohm’s law?

A

For a metallic conductor kept at a constant temperature, the current in the wire is directly proportional to the p.d. across its ends.

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55
Q

Why does resistance increase when heat increases?

A

When heat increases, the positive ions in the metal gain more energy thus vibrate more about their mean positions so the frequency of collisions between the positive ions and charge carriers increases so the charge carriers do more work (transfer more energy) as they travel through the wire.

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56
Q

What does the I-V graph for a fixed resistor look like?

A

Straight line through the origin

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57
Q

What is a resistor called if it obeys ohms law?

A

It is an ohmic conductor.

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58
Q

How does a resistor behave under reversed polarity?

A

The same

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59
Q

What is the relationship between the voltage and current in a filament lamp I-V graph and what does this say about the lamp?

A

Voltage is not directly proportional to current so is a non ohmic conductor and its resistance is not constant.

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60
Q

How does the behaviour of a filament lamp change with polarity?

A

It behaves the same

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61
Q

What is a main reason that LEDs are more effective than other bulbs?

A

They do not get hot so do not have much resistance and draw much less power

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62
Q

What does the I-V graph of a diode look like?

A

Flat up until the origin where it starts to curve upwards before increasing at a linear rate

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63
Q

What is the relationship between the p.d. and current in an LED and what does this say about and LED?

A

P.d. Is not directly proportional to current in an LED and so can be described as a non ohmic conductor

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64
Q

How does the behaviour of an LED change with polarity?

A

A negative voltage will cause an infinite resistance in the LED so it will not work

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65
Q

What is the name of the point on an I-V graph for an LED where the resistance starts to decrease?

A

The threshold p.d.

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66
Q

What three factors (aside from temperature) affect resistance?

A

The material
The length of the wire L
The cross-sectional area of the wire A

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67
Q

What is the relationship between Resistance and the length of a wire?

A

Resistance is directly proportional to the length of a wire (double R = double L)

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68
Q

How is resistance related to cross-sectional area?

A

Resistance is inversely proportional to cross sectional area (2R = 1/2A)

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69
Q

What is the equation for resistivity?

A

R (resistance) = (P (resistivity) x Length) / A (cross-sectional area)

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70
Q

What does it mean if a material has a negative temperature coefficient?

A

It’s resistance drops as the temperature increases

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71
Q

What is a thermistor made of?

A

A material with a negative temperature coefficient

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72
Q

Where are thermistors used?

A

Thermometers
Thermostats
Engine temperature monitors

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73
Q

What does the I-V graph for a thermistor look like?

A

It is an upwards curve (downwards cure in the negative V)

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74
Q

How does the resistance of an LDR change with surrounding conditions?

A

As the surroundings get brighter, resistance decreases

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75
Q

How does an LDR work?

A

When the light intensity increases, the resistance decreases because the number density of charge carriers increases.

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76
Q

Define potential difference

A

The amount of work done per unit charge

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77
Q

Define the volt

A

The potential difference across a component is 1 volt when you do 1 joule of work moving 1 coulomb of charge through a component

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78
Q

Define mean drift velocity

A

The average velocity of all the charge carriers

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79
Q

What are the charge carriers in liquids and gasses?

A

Ions

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80
Q

What does the IV graph for a thermistor look like?

A

It is an upward curve in the top right and a downward curve in the bottom left

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81
Q

Define Power in terms of an electrical circuit

A

Power is the rate of energy transfer

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82
Q

What are 2 equations for electrical power?

A

P = W (work done in watts) / T (time)
P = VI

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83
Q

What is the equation for work done in terms of power?

A

W = Power x Time
Also, W = VIT (voltage x current x time)

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84
Q

When working with power, what should you always look out for?

A

Of the units, most questions deal with kWh but some only Wh

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85
Q

What causes resistance?

A

Electrons collide with atoms and lose energy

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86
Q

How do you calculate the total e.m.f. for cells in series?

A

Add together the individual e.m.f.s of all the cells in parallel

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87
Q

How do you calculate the total e.m.f. for identical cells in parallel?

A

total e.m.f. will equal the e.m.f. of the individual cells (e = e1 = e2 etc)

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88
Q

How can you measure terminal p.d?

A

Attach a voltmeter to the power supply terminals. This will be just slightly less than the e.m.f. due to lost volts.

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89
Q

What is the equation to calculate output voltage in a potential divider circuit? And which resistor is the output attached to?

A

Vout = (R2 x Vin) / (R1 + R2) where R2 is the resistor connected in parallel with a voltmeter

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90
Q

What is a potentiometer?

A

A potentiometer is a potential divider that uses a variable resistor instead of R1 and R2

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91
Q

What ratio describes the distribution of p.d in a potential divider circuit? Explain what it means

A

V1 / V2 = R1 / R2. If a component has a higher resistance then it will receive a higher share of the voltage. Or, the greater the share of the total resistance, the greater the p.d supplied.

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92
Q

What is the name for forces that produce an extension in an object?

A

Tensile forces

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93
Q

What is the name for forces which compress an object?

A

Compressive forces

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94
Q

What happens to a spring when it experiences tensile and compressive forces?

A

Tensile deformation
Compressive deformation

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95
Q

What happens to the force-extension graph of a spring when it reaches its elastic limit? And what does the spring experience past this point?

A

It starts to flatten out and experience plastic deformation

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96
Q

What is elastic deformation?

A

When the shape of an object is deformed but it will still return to its original shape

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97
Q

What is plastic deformation?

A

When the shape of an object is deformed but it will not return to its original shape

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98
Q

When does a spring generally obey Hooke’s law?

A

When it has not yet reached its limit of proportionality.

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99
Q

What is the equation for force in terms of extension? (Hooke’s law)

A

Force = spring constant x extension

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100
Q

What is the spring constant of a spring actually measuring?

A

The stiffness of a spring

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101
Q

How can the spring constant be interpreted?

A

If the spring constant is high, the spring is difficult to extend

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102
Q

What is the gradient of a force - extension graph?

A

The spring constant

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103
Q

What happens to the work done on a material that is extended?

A

If it has not gone beyond its elastic limit, the work done on a material that is extended can be fully recovered

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104
Q

What is the equation for work done in a material that has been extended?

A

Change in W = Force x Change in distance

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105
Q

What is the area under a force - extension graph?

A

The work done on the spring

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106
Q

What is the work done on a spring in order to extend it transferred into?

A

Elastic potential energy within the spring

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107
Q

What is the equation for elastic potential energy and where has it come from?

A

E = 1/2 * F * extension
This is the area under a force extension graph since it will be a triangle

108
Q

What is the equation for elastic potential energy in terms of the spring constant?

A

E = 1/2 * k * extension^2

109
Q

What will doubling the extension of a spring do to its elastic potential energy? Why?

A

Multiply it by 4, since elastic potential energy is directly proportional to extension^2

110
Q

What is the name of the ‘loop’ formed under the force-extension graph of rubber?

A

A hysteresis loop.

111
Q

What does the area inside of a hysteresis loop represent?

A

The thermal energy released in the loading of the rubber material.

112
Q

What is the equation for tensile stress?

A

Stress = force / cross-sectional area

113
Q

What is the equation for tensile strain?

A

Strain = Extension / original length

114
Q

What is it called when a material is stretched and begins to get thinner?

A

Necking

115
Q

What are the 6 major points on a stress strain graph (for steel)? (In order)

A

The limit of proportionality
The elastic limit
Yield points 1 and 2
UTS point
Breaking point

116
Q

What is the limit of proportionality?

A

The point when a material stops obeying Hooke’s law

117
Q

What could define a strong material?

A

One with a high ultimate tensile strength

118
Q

What is the equation for young modulus?

A

Young modulus = Stress / strain

119
Q

When does the young modulus apply?

A

Up to the limit of proportionality of a material

120
Q

What is the unit for the young modulus?

A

Pa or Nm^-2

121
Q

How can you obtain the young modulus of a material from its stress strain graph?

A

By finding the gradient

122
Q

How can young modulus be interpreted?

A

A higher young modulus makes for a stiffer material

123
Q

How can you identify a brittle material from a stress strain graph?

A

A brittle material does not have a curve, the line simply ends when the material snaps

124
Q

What is the elastic limit?

A

The point at on a force-extension graph where if exceeded, a spring will no longer return to its original shape

125
Q

What is the equation for spring constant in a series of springs?

A

1/k = 1/k1 + 1/k2 (the same equation for resistance in parallel)

126
Q

What is the equation for spring constant for springs arranged in parallel?

A

K = k1 + k2

127
Q

What is the ultimate tensile strength of a material?

A

The maximum amount of stress it can endure before necking and breaking

128
Q

How can you measure the young modulus of a wire?

A

Stretch it between to points and mark its length at any point, then find the cross sectional area and total length of the wire. Then add weights to one end and as the wire stretches measured its new weight with each new mass added. Then calculate with this the stress and strain then the young modulus.

129
Q

What is the unit for stress?

A

Nm^-2

130
Q

What is the unit for strain?

A

There isn’t one

131
Q

Def conservation of energy

A

The total energy of a closed system remains constant. Energy cannot be created or destroyed, only transferred from one form to another.

132
Q

Define energy

A

The capacity that something has to do work (since one Joule is equal to one Nm)

133
Q

Def elastic potential energy

A

The energy stored in an object as a result of reversible changes in its shape

134
Q

Def electrical potential energy

A

Energy of electric charges due to their position in an electrical field

135
Q

Def internal (heat or thermal) energy

A

The sum of all the random potential and kinetic energies of the atoms in a system

136
Q

What is important to remember about KE and GPE which is useful in an exam?

A

Loss of GPE = gain in KE, therefore:
mgh = 1/2mv^2 (Cancel the mass)

137
Q

What is the equation for power?

A

P = W / t

138
Q

What other ways could you find the work done in the power equation?

A

Find the change in kinetic energy,
Find the change in GPE
Find the regular work done (force x distance)

139
Q

What is the second equation for power? (In terms of speed)

A

Power = force x speed

140
Q

What is the equation for efficiency percentage?

A

Efficiency = (useful output energy / total input energy) x 100

141
Q

What is the main equation for work done?

A

W = force x distance

142
Q

Define the centre of mass

A

The centre of mass of an object is the mean point of all the mass of an object

143
Q

Define the centre of gravity and where is it?

A

The centre of gravity is the point where the entire weight of an object can be thought to be concentrated. (Appears to act). It is in the same place as the centre of mass.

144
Q

How can you find the centre of gravity of an object?

A

By using 2 points of suspension on a 2D object (flat object) you can use a plumb line to draw a vertical line across the object. The point of intersection of these two lines is the centre of gravity.

145
Q

What are the 6 main forces to be considered in almost any free-body diagram?

A

Weight
Friction
Drag
Tension
Upthrust
Normal

146
Q

What are the two main factors in causing an objects terminal velocity?

A

The objects speed and cross-sectional area

147
Q

What is drag directly proportional to?

A

Speed^2

148
Q

What is the equation for the moment of an object?

A

Moment = force x distance perpendicular to the direction of the line of action of the force

149
Q

What is the unit for a moment?

A

Nm (Newton metre)

150
Q

Define a couple of forces

A

When two equal forces parallel to each other but on different lines that are of equal magnitude affect two different sides of an object causing it to spin without moving (rotating and not translating)

151
Q

What is the torque of a couple?

A

The torque of a couple is the moment between the pair of forces

152
Q

What is the equation for the torque of a couple?

A

Torque (Nm) = Force (N)(of one of the forces) x distance (m)(between the two forces not the centre)

153
Q

What needs to be included alongside the answer and units for a question that wants the torque of a couple?

A

The direction of motion of the torque (clockwise or anti-clockwise)

154
Q

What is an easy way to help visualise and thus solve a triangle of forces question?

A

Draw the completed triangle of forces

155
Q

What is the equation for pressure? (Basic)

A

P = F / A

156
Q

What is the unit for pressure and what is its unit in SI units?

A

Pascals (Pa) or (Nm^-2)

157
Q

What is the equation for the pressure of a vertical column of liquid?

A

P = height x density x g

158
Q

What unusual property is true about the pressure in a fluid?

A

The pressure at any particular depth is the same in all directions.

159
Q

What is the equation for the upthrust of an object underwater and how is this obtained?

A

Upthrust = x (depth of the object) * cross sectional area * density of the fluid * g

This is obtained by subtracting the pressure acting at the top of any object from the pressure acting at the bottom of the object. This is what gives x as distance and not depth since x is the distance between the two places that the pressure is being measured.

160
Q

What is the Upthrust of an object in a fluid equal to?

A

The weight of the the fluid displaced by the object

161
Q

What is archimedes principle?

A

The Upthrust exerted on a body immersed in a fluid wether fully or partially submerged is equal to the weight of the fluid that the body displaces.

162
Q

What could you change in the ball and tube of liquid experiment to affect the balls terminal velocity? (4)

A

Change the liquid
Change the size of the ball
Change the shape of the item being dropped
Change the mass of what’s being dropped

163
Q

What is Archimedes principle?

A

When a body is partially or fully submerged in a fluid, it experiences an upthrust equal to the weight of the fluid displaced

164
Q

What is newton’s 1st law?

A

An object will continue to move with constant velocity or remain at rest unless a resultant force acts upon it.

165
Q

What is Newton’s second law of motion?

A

The rate of change of momentum is directly proportional to the force acting on an object

166
Q

What is Newton’s 3rd law of motion?

A

If object A exerts a force on object B, object B will exert an equal and opposite reaction force on object A, where both forces are of the same type and are along the same line.

167
Q

What is the unit for momentum?

A

Kgms^-1

168
Q

What is the unit for impulse?

A

Ns

169
Q

What’s the equation for momentum (use the generally accepted symbols)

A

P = mv

170
Q

What is the law of the conservation of momentum?

A

Momentum is conserved in any collision provided that no external force acts on the objects.

171
Q

What is the area under a velocity-time graph?

A

Displacement (not distance!)

172
Q

What are thinking distance, breaking distance and stopping distance?

A

Thinking - The time from seeing the obstacle and applying the breaks
Breaking - The time from applying the breaks to coming to a complete stop
Stopping - The time from noticing the obstacle to coming to a complete stop

173
Q

What is the equation for thinking distance?

A

Thinking distance = speed x reaction time

174
Q

Give the two main practical ways of finding the speed of gravity in a lab

A

Using electromagnets and a timer
Using light gates

175
Q

What does the gradient of a displacement-time curve look like when an object is decelerating?

A

It is curving downwards

176
Q

How do you get velocity from a displacement time graph?

A

Find the gradient. Remember v is the differential of s and a is the differential of v

177
Q

What 4 things can affect thinking distance?

A

Tiredness
Alcohol/drugs
Illness
Distractions such as children

178
Q

What 3 things can affect breaking distance?

A

Bad brakes so reduces friction
Wet or icy roads (anything reducing the tyres friction with the road)
The weight of the car (a lighter car has less momentum)

179
Q

define a progressive wave

A

A moving wave that carries energy from one place to another without transferring any material in which the direction of energy transfer is the same as the waves direction of travel

180
Q

def phase difference

A

The amount that one wave lags behind another

181
Q

What is the equation for frequency in terms of the period?

A

Frequency = 1 / Period

182
Q

How does an oscilloscope work?

A

A cathode ray oscilloscope measures voltage. It displays waves from a signal generator as a function of voltage over time.

183
Q

What is the name of the wave on an oscilloscope?

A

A trace

184
Q

What are the squares on an oscilloscope called?

A

Divisions

185
Q

What is the timebase on an oscilloscope?

A

The horizontal axis is the timebase (the amount of time per division)

186
Q

How would you calculate wave frequency from an oscilloscope?

A

Find the period by counting how many divisions in one full oscillation of the wave and then multiply by the timebase. Then do 1 / Period to get frequency.

187
Q

What two dials are on an oscilloscope and can help make them easier to read?

A

The gain dial (changes volts/div) and the timebase dial (changes time(ms)/div)

188
Q

What direction do transverse waves vibrate with respect to the direction of movement?

A

At right angles to the direction of movement

189
Q

What direction do longitudinal waves vibrate with respect to the direction of movement?

A

Parallel to the direction of movement

190
Q

What is the name for the points on a longitudinal wave where the waves are close together and far apart?

A

Compression (close) and rarefaction (far)

191
Q

How can you identify the wavelength of a longitudinal wave?

A

From one compression/rarefaction to another

192
Q

Define the intensity of a wave

A

Intensity is the rate of flow of energy per unit area at right angles to the direction of travel of the wave

193
Q

What is the equation and unit for wave intensity?

A

Intensity (W/m^2) = Power (W) / Area (m^2)

194
Q

Intensity is proportional to…

A

Amplitude squared

195
Q

What types of fields are the waves on the EM spec

A

Electrical and magnetic

196
Q

Can EM waves be polarised?

A

Yes, since they are all transverse

197
Q

What is the full EM spec?

A

Radio, Micro, Infrared, Visible light, Ultraviolet, X-Ray, Gamma

198
Q

What is the approximate wavelength of radio waves? (m)

A

10^-1 - 10^6

199
Q

What is the approximate wavelength of microwaves? (m)

A

10^-3 - 10^-1

200
Q

What is the approximate wavelength of infrared light? (m)

A

7x10^-7 - 10^-3

201
Q

What is the approximate wavelength of visible light? (m)

A

4x10^-7 - 7x10^-7

202
Q

What is the approximate wavelength of ultraviolet light? (m)

A

10^-8 - 4x10^-7

203
Q

What is the approximate wavelength of X-rays? (m)

A

10^-13 - 10^-8

204
Q

What is the approximate wavelength of gamma rays? (m)

A

10^-16 - 10^-10

205
Q

What are some uses of radio waves? (1)

A

Radio transmmissions

206
Q

What are some uses of microwaves? (3)

A

Radar, cooking, TV transmissions

207
Q

What are some uses of infrared light? (4)

A

Heat detectors, night vision cameras, remote controls, optical fibers

208
Q

What are some uses of visible light? (2)

A

Human sight, optical fibers

209
Q

What are some uses of ultraviolet light? (2)

A

Sunbeds, security marks

210
Q

What are some uses of X-rays? (3)

A

Medical imaging, Airport security scanners, radiotherapy (cancer treatment)

211
Q

What are some uses of gamma rays? (3)

A

Irradiation of food, sterilization, radiotherapy (cancer treatment)

212
Q

What can radio waves penetrate through?

A

Matter

213
Q

What can microwaves penetrate through?

A

Mostly matter, but causes heating

214
Q

What can IR light penetrate through?

A

Absorbed by matter but causes heating

215
Q

What can visible light penetrate through?

A

Absorbed by matter but causes heating

216
Q

What can UV light penetrate through?

A

Absorbed by matter but causes some ionisation

217
Q

What can X-rays penetrate through?

A

most matter but causes ionisation

218
Q

What can gamma rays penetrate through?

A

most matter but causes ionisation

219
Q

def polarisation

A

The filtering of transverse waves so that they only pass through a filter if they oscillate in one direction (are able to pass through the filter)

220
Q

def the plane of polarisation

A

The plane which a polarised wave oscillates on (a vertical filter polarises a wave in the vertical plane)

221
Q

def plane polarisation

A

When a wave is polarised to only oscillate in one direction

222
Q

What does the fact that you can polarise light show that light is?

A

It shows that light is a wave (or rather behaves like one)

223
Q

What is the transmission axis of a polarisation filter?

A

Only light oscillating along the transmission axis will pass through (Waves oscillating vertically will be transmitted through a vertical transmission axis)

224
Q

What can you use to polarise microwaves?

A

A metal grille (microwaves have too high a wavelength to be polarised through a polarisation filter)

225
Q

What determines how much waves diffract through a gap?

A

The size of the gap and the wavelength of the travelling wave.

226
Q

At what point can you observe the most diffraction when changing the size of the gap in an experiment?

A

When the size of the gap is the same as the wavelength of the travelling wave.

227
Q

What happens if the size of a gap for diffraction is smaller than the wavelength?

A

The waves get reflected back on themselves

228
Q

Why can you hear someone round a doorway but not see them?

A

Sound waves have similar wavelengths to the size of doorways and so diffract a lot but light waves are far too small to cause noticeable diffraction

229
Q

What two experiments could you do to show light diffracting?

A

Shine a laser through a very small slit or shine white light through a colour filter.

230
Q

def reflection

A

When a wave is bounced back upon hitting a boundary where the angle4 of incident is equal to the angle of reflection.

231
Q

def refraction

A

The change in the direction of movement of a wave as a result of entering a different medium.

232
Q

Why does the wave speed change during refraction?

A

The wavelength changes but the frequency remains constant.

233
Q

def optical density

A

The amount that a material slows down light. A higher optical density means light travels slower through it.

234
Q

what is the equation for refractive index?

A

n (refractive index) = c (sol in a vacuum) / v (sol in that material)

235
Q

What is Snell’s law

A

n1sinA1 = n2sinA2

236
Q

def total internal reflection

A

When all of the light is reflected back into the material and not refracted

237
Q

What is a critical angle? (refraction)

A

The angle at which light stops being refracted and is only internally reflected if it gets any larger

238
Q

What is the equation for the critical angle for light within a material to air boundary?

A

SinC = 1/n

239
Q

def superposition

A

When to waves cross, the displacement as any point is the sum of the two individual displacements

240
Q

def interference

A

When two or more waves superimpose with each other

241
Q

def constructive interference

A

When waves ‘combine’ to increase the original displacement. i.e. a crest and a crest or a trough and a trough

242
Q

def destructive interference

A

When two waves superimpose at a point to create nothing i.e. a crest ‘combines’ with a trough of equal size and results in 0 displacement

243
Q

what does it mean if interference isn’t ‘total’?

A

The two parts of the waves are not of equal magnitude and so don’t completely cancel out or completely double in displacement.

244
Q

def ‘in phase’

A

two points on a wave are in phase if they are at the same point of the wave cycle i.e. two crests

245
Q

what property to points that are in phase have?

A

The same displacement and velocity

246
Q

def phase difference?

A

The difference in position (x-axis) of two points

247
Q

def coherence

A

When two waves have the same wavelength and frequency and a fixed phase difference

248
Q

def path difference

A

For two wave sources that are in phase and coherent, the path difference is just how much further one wave has travelled compared to another to get to that point.

249
Q

At what amount of path difference can you observe constructive interference?

A

When the path difference is a whole number of wavelengths

250
Q

At what amount of path difference can you observe destructive interference?

A

When the path difference is an odd number of half wavelengths.

251
Q

What is the equation for wavelength that links fringe spacing and the distance from a slit to a screen?

A

λ = (a (slit separation) * x (fringe separation)) / D (distance from slits to screen)

252
Q

What effect does diffracting through more than two slits have in comparison to diffracting through only two slits?

A

The fringes are brighter and more defined (narrower).

253
Q

When shining light through a diffraction grating, what effect does a longer wavelength light cause?

A

The pattern will be more spread out

254
Q

What happens when white light is shone through a diffraction grating?

A

Each maxima (order) is a spectra from red on the outside (side furthest from central maxima) and violet on the inside (side closest to central maxima)

255
Q

Do stationary waves transmit energy?

A

Nuh uh

256
Q

How is a stationary wave formed when only one signal generator is present?

A

The waves generated travel out and then reflect back perfectly to create a standing wave

257
Q

On a standing wave, where are the nodes and where are the antinodes?

A

Nodes are where the waves meet, antinodes are where the waves are at a greatest distance.

258
Q

Define resonant frequency in terms of a number of wavelengths.

A

In order to achieve a resonant frequency, an exact number of half wavelengths fit into the space that a wave has to oscillate. Or in the string experiment, an exact number of half wavelengths fit onto the string.

259
Q

If a tube is open at both ends and a standing wave is within it, what type of node would be at each end?

A

Antinode

260
Q

If a tube is closed at both ends and a standing wave is within it, what type of node would be at either end?

A

Node

261
Q

What is the area under a force-time graph equal to

A

The impulse

262
Q

What happens to energy and momentum in a perfectly elastic collision?

A

Momentum and kinetic energy are both conserved. I.e. no energy is dissipated as heat or sound

263
Q

What happens to energy and momentum in an inelastic collision?

A

Some kinetic energy will be converted to other forms during the collision but momentum is still conserved

264
Q

What is the point of air bags, crumple zones and seatbelts in a collision?

A

They slow you down gradually, therefore reducing the change in momentum (impulse) that you experience

265
Q

Why are seatbelts risky in some cases? (2)

A

They can cause bruising during a crash
They can be dangerous for small children and if the seatbelt is seated at their neck can be fatal

266
Q

Why are airbags risky during a crash in some cases?

A

If not wearing a seatbelt, a passenger can hit a rapidly expanding airbag very quickly and can be seriously injured by the bag.
For a rear facing booster seat, an airbag can push the seat towards the car seat with a lot of force and kill the child

A Level OCR Physics (15 decks)

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