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Waves Flashcards

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1
Q

What is a wave’s amplitude?

A

The amplitude of a wave is its maximum displacement from its equilibrium position

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2
Q

What is a wave’s frequency?

A

The number of complete waves that pass a point per second

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3
Q

What is the period of a wave?

A

THe length of time taken for one complete wave to pass a given point

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4
Q

How are frequency and period linked?

A

f = 1/T

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5
Q

What is wavelength?

A

Distance between the same point on 2 adjacent waves

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6
Q

What is the equation for wave speed?

A

v = fλ

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7
Q

Describe a longitudinal wave

A

Particle oscillations are parallel to direction of the wave’s motion
Consists of rarefactions (low pressure regions), and compressions (high pressure regions)

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8
Q

Describe a transverse wave

A

Particles oscillations are perpendicular to the wave’s motion
Consists of peaks (max positive displacement) and troughs (max negative displacement)

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9
Q

What is a progressive wave

A

A wave that transfers energy from one point to another without any transfer of matter

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10
Q

What is a standing wave

A

A wave that stores energy instead of transferring it from one place to another

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11
Q

What is path difference a measure of

A

How far ahead one wave is compared to another

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12
Q

What is a wave’s phase

A

A measure of how far through its cycle the wave is. Usually measured in radians 1 cycle = 2π

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13
Q

What is the phase difference between 2 waves at a given point

A

The difference between 2 waves at a given point

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14
Q

What happens when 2 waves meet

A

Interference occurs

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15
Q

What happens when 2 waves meet in phase

A

They will interfere and undergo constructive interference

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16
Q

What happens when 2 waves meet in antiphase

A

They will interference and undergo destructive interference

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17
Q

How is a standing wave formed on a string

A

A wave reflects from a closed end meaning 2 identical waves are travelling in opposite directions down the same string
At points where the waves meet in phase, constructive interference occurs and an antinode is formed
At points where waves meet in antiphase, destructive interference occurs and a node is formed

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18
Q

What is a node

A

A point of minimum displacement

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19
Q

What is an antinode

A

A point of maximum displacement

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20
Q

What factors does the speed of a transverse wave on a string depend on

A

Time period

Mass per unit length of string

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21
Q

State the equation used to calculate speed of transverse wave on a string

A

v^2 = T/μ

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22
Q

What is the equation used to calculate intensity

A

I = P/A

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23
Q

What is the refractive index of a material through which light travels a speed of ‘v’

A

n = c/v

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24
Q

State the equation linking refractive indexes and angles at an interface in 2 different mediums

A

n1 sinθ1 = n2 sinθ2

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25
Q

What is the critical angle

A

The angle of incidence for which the angle of refraction is 90° and all the light passes along the boundary between the mediums. Beyond this angle all light will be reflected.

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26
Q

State the equation used to calculate critical angle

A

sinC = 1/n

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27
Q

What is TIR

A

Where all light is reflected back at the boundary between 2 mediums. It occurs when the angle of incidence is greater than c

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28
Q

What is the focal point of a converging lens

A

The single point where the parallel rays of light entering the lens converge to

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29
Q

What is the focal length of a lens

A

The distance between the centre of the lens and the focal point

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30
Q

What is the equation for power of a lens

A

Power = 1/ focal length

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31
Q

How do you calculate the total power of a combination of thin lens

A

P = P1 + P2 + P3…

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32
Q

What is a real image

A

An image that can be projected onto a screen and is always inverted after light has met at a focal point

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33
Q

What is a virtual image

A

Virtual images are the consequence of light appearing to meet at a point. They cannot be projected onto a screen.

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34
Q

State the equation for magnification of an image

A

Magnification = Image height / Object height

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35
Q

What is plane polarisation

A

When oscillations of a wave are restricted to a single plane

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36
Q

What is diffraction

A

The spreading out of a wave as it passes through a gap

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37
Q

What criteria must be met for maximum diffraction to occur

A

The size of the gap must be the same as the wavelength of the wave

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38
Q

What happens if the gap is much smaller than the wavelength of the wave

A

The wave will be reflected

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39
Q

State the diffraction grating equation

A

nλ = dsinθ

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40
Q

What does electron diffraction provide evidence for

A

The wave nature of electrons. It suggests that particles have wave properties.

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41
Q

Describe the diffraction pattern produced by electrons

A

Concentric circle of a bright and dark fringes from a central bright point

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42
Q

If electrons didnt have a wave nature, describe the pattern that would be produced when they pass through a slit

A

The electrons would be unaffected by the gap and pass straight through. A single bright region would be formed

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43
Q

What is the name given to the wavelength of a particle

A

De Broglie wavelength

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44
Q

What 2 factors does the de Broglie wave length depend on

A

Mass

Velocity

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45
Q

State the equation for de Broglie wavelength

A

λ = h/mv

h is Plank’s constant

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46
Q

What can mv be replaced with in the de Broglie equation

A

momentum

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47
Q

What is the basic process of a pulse-echo technique

A

A wave pulse is emitted
It is transmitted and reflected at the boundary between 2 mediums
The returning wave (echo) is detected
The speed and time are used to calculate distance to the object

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48
Q

Suggest 2 things that may limit the amount of information that can be obtained by a pulse-echo technique

A

The wavelength of the radiation

The duration of the pulse

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49
Q

What are the 2 models that can be used to describe EM radiation

A

Wave model

Particle model

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50
Q

Which model does the photoelectric effect provide evidence for

A

The particle model

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51
Q

Outline the photoelectric effect

A

Light is shone on a metal plate
IF the light has a high enough frequency, electrons are emitted from the metal surface
If the frequency is too low, no electrons are emitted

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52
Q

What are particles of light used to explain the photoelectric effect called

A

Photons

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53
Q

How do you calculate the energy of a photon

A

E = hf

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54
Q

Explain how a photon can liberate an electron

A

One photon interacts with one electron and transfers all its energy to it. If this energy is greater than the metal’s work function, the electron will have sufficient energy to be released

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55
Q

What is threshold frequency

A

A metals threshold frequency is the minimum frequency that a photon required to liberate an electron from its surface

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56
Q

If the intensity of light being shone on a metal increases, how does the energy of the photoelectrons change

A

The energy remains unaffected. An increase in intensity means more photons per area and so more photoelectrons are emitted

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57
Q

Why are photoelectrons emitted with a range of kinetic energies

A

Electrons are at different depths in the metal and so require different amounts of energy to be liberated. The excess energy from a photon once an electron has been liberated, is the kinetic energy of the electron

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58
Q

State the equation for the minimum kinetic energy of a photo electron

A

1/2 mv^2max = hf - Φ

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59
Q

What is the conversion factor between eV and J

A

1eV = 1.6x10^-19 J

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60
Q

What happens when electrons transition between energy levels

A

If electrons move to a higher energy level, radiation must be absorbed
If electrons move to a lower energy level, radiation is emitted

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61
Q

Why can only certain frequencies of radiation be absorbed by an atom to cause an electron transition

A

The electron can only exist in discrete energy levels. The energy of the photon absorbed must be the exact same amount of energy required to cover the difference between the two discrete energy levels

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62
Q

What is the difference between a base unit and a derived unit

A

A base unit is one of 7 fundamental units. A derived unit is derived from multiplication or division of units
A unit is a measure of quantity

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63
Q

What is the order of the scale units

A 
Pico x10^-12
Nano x10^-9
Micro x10^-6
Milli x10^-3
Centi x10^-2
Kilo x10^3
Mega x10^6
Giga x10^9
Terax10^12
64
Q

What is the difference between independent and dependent variables

A

Independent- what you change in an investigation and normally cause the effect on the dependent
Dependent- what is observed/measured

65
Q

What is the difference between precision and accuracy

A

Precision is how consistent results are.

Accuracy is how close the results are to the true value

66
Q

What is the difference between error and uncertainty

A

Error is the difference between the measurement and the true value
Uncertainty is the interval within which the true value can be considered to lie within a given level of probability

67
Q

How do you calculate % uncertainty

A

uncertainty of measurement/measurement (x100)

68
Q

How can you tell if a value is an anomaly

A

If it does not follow the pattern of results

69
Q

What happens to the absolute uncertainty when you add/subtract/multiply or raise to a power?

A

Add/subtract: add uncertainties
Multiply: multiply uncertainty by constant
Raise to a power: raise uncertainty to same power

70
Q

What happens to the % uncertainty when you add/subtract/multiply or raise to a power?

A

Add/subtract: add % uncertainties
Multiply: doesn’t change
Raise to a power: multiply by index

71
Q

What is the difference between repeatable and reproducible

A

Repeatable measurements are when similar results can be obtained by students from the same group using the same method
Reproducible measurements are when similar results are obtained by students from different groups using different methods/apparatus

72
Q

How can validity be improved

A

Control more variables
Use more precise measuring equipment
Obtain more results to reduce uncertainty

73
Q

What is the difference between systematic and random errors

A

Random errors are caused by unpredictable changes in the investigation, often caused by the environment or irregular changes. Usually impact precision

Systematic errors are continuous errors throughout, often caused by equipment. Usually impacts accuracy

74
Q

What is the density of a material

A

The density is the mass per unit volume

75
Q

What is the equation for density

A

Density = mass/volume

76
Q

What is the unit of density

A

kgm^-3

77
Q

When an object is submerged in a fluid, what determines the upthrust that acts on it

A

Upthrust = weight of fluid that it displaces

78
Q

What determines whether an object floats or sinks

A

The balance between the weight and upthrust of the upthrust. If weight > upthrust, the object will sink

79
Q

Why will a uniform object, with a density greater than that of the fluid it is submerged in, always sink

A

Upthrust = Weight of fluid displaced
Max upthrust = fluid density x object volume x g
Object weight = object density x object volume x g
If object density >, the weight will always be greater than upthrust and the object will sink

80
Q

What objects does Stokes’ Law apply to?

A

Small and spherical in laminar flow

81
Q

What does Stokes’ law calculate

A

The viscous drag force that a small spherical object experiences at low speeds in a viscous fluid wuth laminar flow

82
Q

State the equation for Stokes’ Law

A

F=6πrηv

83
Q

What is elastic deformation

A

When an object returns to its original shape once the deforming forces are removed

84
Q

What is plastic deformation

A

When an object no longer returns to its original shape once deforming forces are removed. It will be permanently deformed

85
Q

What is Hooke’s Law

A

The extension of an elastic object is directly proportional to the force applied, up to its limit of proportionality

86
Q

What is the limit of proportionality

A

The point beyond which the force applied and extension are no longer directly proportional to each other

87
Q

What is the elastic limit

A

The point beyond which the object will no longer elastically deform, and instead plastically deforms

88
Q

What is the equation for Hooke’s Law

A 
F = kΔx
F = force applied (N)
k = stiffness constant
Δx = extension (m)
89
Q

What is mechanical stress

A

The force experienced by an object per unit area

90
Q

What is the equation for stress

A

Stress = F/A

91
Q

What is the unit for stress

A

Nm^-2

92
Q

What is the equation for strain

A

Strain = ΔL/L

93
Q

What is the unit for strain

A

It is unitless as it is the ratio of 2 lengths

94
Q

What does the Young’s Modulus of a material tell you

A

How much force is required for a given extension, regardless of dimensions

95
Q

What is the equation to calculate a material’s Young’s Modulus

A

Young’s Modulus = Stress/Strain

96
Q

What is the unit for Young’s Modulus

A

Nm^-2

97
Q

What is breaking stress

A

The maximum stress that an object can withstand before fracturing

98
Q

What is the yield point

A

The point beyond which the object will experience a large extension without substantial force being applied

99
Q

What type of energy is stored in an object that has been stretched

A

Elastic Potential Energy

100
Q

What are the 2 equations for energy stored in a spring

A 
E = 1/2FΔx
E = 1/2kΔx^2
101
Q

What does the gradient and area represent on a force- extension graph

A 
gradient = elastic constant
area= elastic potential energy in the spring
102
Q

Define electrical current

A

The rate of flow of charge

103
Q

What is the equation for current

A

I = Q/T

104
Q

What is the unit for current

A

Ampere (A)

105
Q

Define Voltage

A

Work done per unit charge

106
Q

What is the equation linking voltage work done and charge

A

V = W/Q

107
Q

What is the equation linking V, I and R

A

V = IR

108
Q

What is Ohm’s law?

A

The current and voltage passing through a component is directly proportional when at a constant temperature

109
Q

Describe the distribution of current in a series circuit

A

The current is the same at all positions in the circuit

110
Q

What law is the distribution of current in a series circuit a consequence of

A

The law of conservation of charge

Charge cannot be created or destroyed, so in a closed loop the flow of charge must be equal throughout

111
Q

Describe the distribution of current in a parallel circuit

A

It is split between the different branches

Current entering a branch = current leaving a branch

112
Q

Explain how the conservation of charge applies to parallel circuits

A

Charge cannot be created or destroyed so the total charge leaving a source must equal the sum of currents in all individual branches

113
Q

What law is the distribution of potential differences in a circuit the consequence of

A

The law of conservation of energy

114
Q

Describe the distribution of potential differences in a series circuit

A

The total potential difference is split across all the components in a series circuit, in the ratio of their resistances

115
Q

Describe the distribution of potential differences in a parallel circuit

A

The sum of potential differences in each branch of a parallel circuit is the same and will be equal to the potential difference of the source

116
Q

What equation links power current and potential difference

A

P = IV

117
Q

How can you calculate work done over a given time period by a component with a known potential difference and current

A

Combine the two equations P=W/t and P=IV

W = IVt

118
Q

Describe the IV graph of an ohmic conductor

A

A straight line through the origin where I is directly proportional to V

119
Q

Describe the IV graph of a filament bulb

A

An S shape with a constant gradient in the middle going through the origin

120
Q

Describe the IV graph of a diode

A

An almost horizontal line with a slight positive gradient until part way through the positive values of V where the gradient curves upwards into a steeper positive constant gradient

121
Q

Explain the IV graph of a filament bulb

A

Higher current causes higher temperature in the metal filament
Higher temperature causes higher KE in metal IONs so they vibrate more
This makes it more difficult for current to flow so the bulb’s resistance increases

122
Q

What must be true when using the SUVAT equations of motion

A

Acceleration must be constant

123
Q

What does the gradient of a distance-time graph represent

A

Speed

124
Q

What does the gradient of a displacement-time graph represent

A

Velocity

125
Q

What does the gradient of a velocity time-graph represent

A

Acceleration

126
Q

Describe the shape of a velocity-time graph for an object travelling with uniform acceleration

A

If acceleration is constant, the gradient will be constant so it will be a straight line graph

127
Q

Describe the shape of a velocity-time graph for an object travelling with non-uniform acceleration

A

The gradient (acceleration will change so will form a curve

128
Q

Compare the velocity time graphs for uniformly accelerating and uniformly decelerating objects

A

Accelerating : positive gradient

Decelerating: negative gradient

129
Q

What is a scalar quantity

A

A quantity with magnitude but no fixed direction

130
Q

What is a vector quantity

A

A quantity with magnitude and a fixed direction

131
Q

How is a vector represented on a diagram

A

As an arrow
The arrows direction shows the objects direction
The length of the arrow shows the object magnitude

132
Q

What does resolving a vector involve

A

Splitting a vector into 2 perpendicular components

133
Q

Describe the relationship between the perpendicular components of a vector

A

They are independent of each other

134
Q

How should the components of a projectile be handled when carrying out calculations

A

Horizontal and vertical components should be treated separately
SUVAT should be used for each component

135
Q

What three physical factors affect the resistance of a wire

A

Length
Cross sectional area
Resistivity

136
Q

How does increasing length of a conductor affect its resistance

A

The longer a conductor is, the higher its resistance

No other factors are affected

137
Q

How does increasing the cross sectional area of a conductor affect its resistance

A

The larger the cross sectional area, the lower the R

No other factors are affected

138
Q

What is resistivity

A

A characteristic of a material that determines its resistance to flow of current

139
Q

Compare the resistance of 2 conductors of the same dimensions, but with different resistivities

A

The conductor with higher resistivity will have higher R

140
Q

State the equation for resistance using resistivity

A

R = ρl/A

141
Q

What equation links number of charge carriers in a metal with drift velocity with current flow

A

I = nqvA

142
Q

How does the potential along a uniform current-carrying wire cary as you move along it

A

The potential will increase as you move the wire

143
Q

What is the EMF of a power supply

A

The amount of energy that is transferred to each Coulomb of charge that passes through it

144
Q

What is the terminal pd of a power supply

A

The actual potential difference that is produced across the terminals and is provided to the circuit

145
Q

Why does the EMF of a supply differ from its terminal pd

A

Some of the energy that is transferred to the charges is used to overcome the internal resistance of the power supply

146
Q

Define internal resistance in a power supply

A

The electrical resistance when a current flows due to the materials within the supply itself

147
Q

Describe a method to determine the terminal potential difference of a battery

A

Attach a voltmeter directly across the terminals of the battery when it is isolated
As no current flows, no potential is lost due to internal R so the voltmeter will read the value of the terminal pd

148
Q

What is a semiconductor

A

A component that can change its R based on external conditions

149
Q

Give 2 examples of semiconductors and what they are sensitive to

A

Thermistor- temperature

LDR- light

150
Q

Describe how the resistance of a thermistor changes as temp decreases

A

As temperature decreases, R in a thermistor increases

151
Q

Explain why the R of a thermistor will decrease with an increase in temperature

A

As temp increases, conduction electrons are liberated, meaning there are more charge carriers and current can flow more easily

152
Q

Describe how the R of a LDR changes as light intensity increases

A

As light increases, the R of a LDR will decrease

153
Q

What is a potential divider

A

A pair of resistors used to split the pd over them in a given ratio

154
Q

What is the link between resistances and the pd in a potential divider

A

The pd of the circuit is split in the ratio of the resistance of the resistors

155
Q

How would the pd over a fixed resistor in series with a LDR change as the light intensity increases

A

As light intensity increases, the R over the LDR will decrease
The fixed resistor will take a larger ration of the circuit potential and the pd will increase

156
Q

Define wave front

A

Line joining points that are in phase

Physics A Level (1 decks)

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