Post Past Paper 1

Question 1

What is the only interaction which can change the quark structure?

Answer 1

Weak interaction

Question 2

Why should all electrons have the same energy during beta decay?

Answer 2

Due to the conservation of momentum

Question 3

What happens to the waves that meet in phase and antiphase when producing a stationary wave?

Answer 3

Waves in phase constructively interfere - creating antinodes (Points of max amplitude)

Waves in antiphase destructviely interfere - creating nodes (Points of min displacement)

Question 4

How can we determine whether a given frequency will produce a stationary wave in a pipe with one closed end?

Answer 4

Standing waves are setup when λ = λ/4, 3λ/4, 5λ/4

Hence the frequencies are odd multiples of the lowest frequency: f, 3f, 5f

If the given frequency is not an odd multiple, it wil not produce a standing wave in a pipe with one closed end.

Question 5

How can we determine whether a given frequency will produce a stationary wave in a pipe with two closed end?

Answer 5

Standing waves are setup when λ = λ/2, λ, 3λ/2

Hence the frequencies are odd multiples of the lowest frequency: f, 2f, 3f

Question 6

How does air resistance affect the path of a ball kicked into the air?

Answer 6

Air resistance acts in the opposite direction to velocity therefore the ball does work against the air resistance and thermal energy is dissipated.
This means GPE gained will be less and the max height of the ball will be less.

Question 7

How is a short circuit and an open circuit achieved?

Answer 7

Short: Very low resistance wire between the terminals.
Open: Set the resistance very high.

Question 8

How is the current found on an IV graph for a given resistance?

Answer 8

Draw a line with the gradient as the reciprocal of the given resistance, take the point where both lines connect.

Question 9

What interaction do Leptons not experience?

Answer 9

The strong interaction

Question 10

What relationship should be true for two rays to give a maximum intensity?

Answer 10

The path difference should be a whole number of wavelengths

Question 11

What is the area under a stress strain graph?

Answer 11

The energy stored per unit volume when a thin wire is stretched.

Question 12

What is material dispersion?

Answer 12

Waves of different wavelengths travel at slightly different speeds through an optical fibre therefore they will reach the end at slightly different times, this causes pulse broadening.
Monochromatic light stops this.

Question 13

What is modal dispersion?

Answer 13

Waves enter an optical fibre at slightly different angles therefore the distance each beam has to travel is slightly different. This also leads to pulse broadening as beams reach the end at slightly different times.

Question 14

Why does the refractive index of the cladding need to have a lower refractive index than the core?

Answer 14

A lower refractive index is needed for TIR to occur and TIR is needed in order to keep the light ray inside and maintain the signal.

Question 15

How can you determine the refractive index of a material using a semi-circular prism?

Answer 15

Using a protractor and a ray box on white paper, reposition the incident ray until the angle of refraction is 90 degrees.
Then, measure the angle of incidence and sub it into (1/sinθ) to find the refractive index.

Question 16

Why may the voltmeter read zero if the resistances across a potential divider are the same?

Answer 16

If the resistances are the same, the ratios between the EMF will also be the same. This means that the potential difference will be zero.

Question 17

What is a fundamental particle?

Answer 17

A particle which is NOT made of smaller component particles (quarks)

Question 18

What are all of the possible conservation laws?

Answer 18

Charge
Baryon Number
Lepton Number
Strangeness
Momentum
Mass-Energy

Question 19

How can you find the maximum height from a vertical velocity against time graph?

Answer 19

Find the area above the x-axis

Question 20

Why would changing the launch height of a projectile affect the horizontal distance?

Answer 20

Greater launch height would give a greater time of flight.
As the horizontal velocity is still constant, it would travel further horizontally.

Question 21

Why would radio reception exactly halfway between two transmitters be particularly good?

Answer 21

Waves would interfere constructively since the path difference and phase difference are both zero.

Question 22

If the signal strength at a point is at a minimum, what happens if the frequency of the radio waves are doubled?

Answer 22

Wavelength would be halved.
At a minimum, the path difference is an odd number of wavelengths.
When wavelength is halved, the new path difference will be an integer therefore maximum signal.

Question 23

What is the difference between a line spectrum and a continuous spectrum?

Answer 23

Line spectrums involve specific wavelengths however, continuous spectrums involve all wavelengths.

Question 24

Why does low pressure hydrogen emit light when a high potential difference is applied across it?

Answer 24

Electrons are accelerated towards the postitive electrode.
These electrons collide with hydrogen electrons and excite them.
They then de-excite and a photon is emitted.

Question 25

What relationship must be followed for a maximum intensity beam?

Answer 25

The path difference must equal a whole number of wavelengths

Question 26

How does the energy stored in a mass spring system in SHM change when it rises from its lowest to its highest point?

Answer 26

GPE increases and Elastic PE decreases.
KE increases until equilibrium and then decreases until it reaches maximum.

Question 27

What is the area under a force time graph?

Answer 27

The change in momentum

Question 28

Why can we not use V = IR to determine what happens to the voltage when the resistance decreases?

Answer 28

Decreasing the resistance increases the current therefore it is unknown as to what happens to the voltage.
In most cases V = ϵ - Ir needs to be used.

Question 29

How do you find the EMF of a circuit?

Answer 29

Find the sum of the pd’s across each component in the circuit.

Question 30

Why does an increase in heat typically lead to an increased resistance in terms of particles?

Answer 30

Lattice ions are more likely to obstruct electrons through the filament.

Question 31

Why can’t longitudinal waves be polarised?

Answer 31

Longitudinal waves can only have oscillations parallel to the direction of energy propagation therefore, a polarising filter would have no effect as the waves already travel in a single direction.

Question 32

What is the formula for mass per unit length?

Answer 32

Area x Density

Question 33

What is an antiparticle?

Answer 33

Every particle has an antiparticle which has the same rest energy and mass but all other properties are opposite of the respective particle.

Question 34

What happens to the central diffraction maximum as you increase the slit width?

Answer 34

It becomes narrower and more intense as less diffraction occurs.

Question 35

How can modal dispersion be reduced?

Answer 35

Use single mode fibres with very narrow paths so the possible difference in path lengths is smaller.

Question 36

What are 5 advantages of optical fibres over traditional copper wires?

Answer 36

Signal can carry more info as light has higher frequencies.
No energy lost as heat.
No electrical interference.
Cheaper.
Faster.

Question 37

What are 2 applications of diffraction gratings?

Answer 37

Splitting up light from stars to make line absorption spectra and identify the elements present within them.
X-ray crystallography to find the spacing between atoms.

Question 38

If radio waves are reflected off of a metal plate between the transmitter and receiver, why may a minimum signal not be exactly zero?

Answer 38

The metal plate could absorb some of the waves which means that the waves do not have equal amplitudes therefore will not completely destructively interfere.

Question 39

How does the intensity of incident radiation affect the rate of discharge of photoelectrons if the threshold frequency is met?

Answer 39

Greater intensity means more photons are incident per second. As each photon ejects one electron, there will be a greater rate of discharge.

Question 40

If the reaction force is greater than the weight of an object, what does this tell you about the acceleration?

Answer 40

As the resultant force is upwards, the acceleration is also upwards.

Question 41

For two wave sources to be coherent what conditions must be followed?

Answer 41

They must have the same frequency and a constant phase relationship.

Question 42

What can be done to increase the amount of orders visible on a diffraction grating?

Answer 42

Increasing the slit separation

Question 43

How does light from a diffraction grating form a maximum on a screen?

Answer 43

As the path difference will be a whole number of wavelengths, the waves will arrive at the screen in phase and superpose (Constructive Interference)

Question 44

What is the difference between an absorption spectrum and an emission spectrum?

Answer 44

In an absorption spectrum, an atom will absorb photons and become excited, these absorbed photons are seen as the missing lines on the continuous spectrum.
In an emission spectrum, excited atoms de-excite and emit a photon of a specific wavelength, producing a coloured line on the black spectrum.

Question 45

What is the EMF of a circuit?

Answer 45

The total energy supplied to each coulomb of charge by the battery (Total V available)

Question 46

What is the terminal p.d.?

Answer 46

The circuit voltage (Would be equal to the EMF if there was no internal resistance)

Question 47

How many maxima are produced by a 4th order diffraction grating?

Answer 47

9 - 4 maxima on either side of the central maxima (4+4+1)

Question 48

How do you calculate the change in momentum?

Answer 48

m(v-u) - The mass multiplied by the rebound velocity minus the impact velocity.

Question 49

What strangeness does a positive Kaon have?

Answer 49

+1

Question 50

What signal would a receiver detect as the path difference of two different wave sources increase?

Answer 50

When the path difference is at a whole number of wavelengths, the signal received will be at a maximum as the waves have constructively interfered.
As the path difference increases, once it reaches (n+1/2) of a wavelength, the signal will be at a minimum since the waves interfere destructively.
This means the signal will constantly vary from maximum to minimum.

Question 51

What condition must be met for the Young’s Double Slit equation to be valid?

Answer 51

As it is an approximation, the distance from the slits to the screen must be much greater than the slit width.

Question 52

During projectile motion, when is the minimum speed of the ball achieved?

Answer 52

It is achieved at the apex as there is no vertical component to velocity therefore it is the horizontal component.

Question 53

How do you determine whether points on a stationary wave are in phase?

Answer 53

If they are on the same side of equilibrium, they are in phase.

Question 54

What pattern would be produced on a screen if white light is shone through a single slit with a green filter in front of it?

Answer 54

Primarily green fringes would be produced on the screen (Maxima + Minima) due to constructive and destructive interference.
All fringes will have the same width apart from the central maxima which is double the width of the rest.
The central fringe is also the brightest with less intense maxima at either side.

Question 55

What happens to a diffraction pattern if the green filter in front of the light source is replaced with a red filter?

Answer 55

The central maxima will be wider and the fringes either side of it will be further apart.