AQA GCE AS Level Physics AS Paper 2 November 2020 question paper 7407/2

A student places a transparent semicircular block on a sheet of paper and draws around the block. She directs a ray of light at the centre of the flat edge of the block.

Figure 1 shows the path of the ray through the block.

State why the emergent ray does not change direction as it leaves the block.

The student draws an arrow on the paper to mark the incident ray. She marks the path of the emergent ray with crosses A, B and C.

She removes the block from the paper and places a protractor over the outline of the block, as shown in Figure 2.

Figure 2

Determine, using Figure 2, the refractive index of the block.

The student uses a different method to determine the refractive index of the block. She focuses a travelling microscope on some dots on a sheet of paper for each of the three situations shown in Figure 3.

Table 1 shows the readings made by the student.

The refractive index n of the block is given by

Determine n.

The absolute uncertainty in each of the readings R₀, R₁ and R₂ is 0.04 mm.

State the absolute uncertainty in R₂ – R₀.

The absolute uncertainty in R₂ – R₁ is the same as the absolute uncertainty in R₂ – R₀

Calculate the percentage uncertainty in n.

Figure 4 shows a circuit used by a student to determine the emf and the internal resistance of a cell.

The cell is connected to a switch, a fixed resistor and a variable resistor. When the switch is closed, a voltmeter measures the potential difference V across the cell. An ammeter measures the current I in the circuit.

Readings of V and I are taken as the resistance of the variable resistor is changed from zero to its maximum value.

Explain why the student included the fixed resistor in this circuit.

Figure 5 is a graph of the data recorded for this experiment.

Determine the magnitude of the minimum gradient G_min of a line that passes through all the error bars in Figure 5.

The maximum gradient G_max / V A⁻¹ of a line passing through all the error bars in Figure 5 is –1.3

Determine, using G_max and G_min, the internal resistance of the cell.

The line of best fit passes through the data point (0.94, 0.37).

Determine the emf of the cell.

Figure 6 shows a camera filming a sports event from above. The position of the camera is controlled by two steel cables, A and B, that pass over fixed, smooth pulleys.

In Figure 6 the camera is stationary. The tension in A is 430 N and A makes an angle of 35 ° to the horizontal. B makes an angle of 12 ° to the horizontal.

Calculate the tension in B.

The cross-sectional area of A is 7.0 × 10⁻⁶ m². The unstretched length of A is 150 m

Calculate the extension of A when the tension in it is 430 N.

Young modulus of steel = 210 GPa

The camera is moved horizontally to the right to a new stationary position. The tension in A is now different from that in Figure 6.

Deduce whether the tension in A has increased or decreased.

The camera’s signal is transmitted as a series of pulses through an optical fibre. Table 2 shows data for two optical fibres X and Y. Both optical fibres are identical except for their core diameter.

Deduce which fibre allows a greater pulse transmission rate.

Scintillation counters are used to detect beta particles. A scintillation counter consists of a scintillation material and a photomultiplier tube (PMT).

Beta particles collide with atoms in the scintillation material, which emits photons of light as a result.

Explain how photons are produced by collisions between beta particles and atoms.

A photon of light from the scintillation material enters the PMT, as shown in Figure 7. The front of the PMT contains a thin photocathode. The photon strikes the photocathode to release an electron.

The longest wavelength of light that releases an electron from this photocathode is 630 nm.

Calculate the minimum photon energy required to remove an electron from the photocathode.

The PMT consists of an evacuated glass tube containing the photocathode, an anode and three metal electrodes, as shown in Figure 8.

The electrodes, anode and photocathode are connected to a potential divider consisting of four identical resistors R. The emf of the electrical supply is 3.0 kV.

The potential difference between the photocathode and the first electrode accelerates the electron along the path shown in Figure 8.

Calculate, in J, the maximum kinetic energy transferred to the electron when it accelerates from the photocathode to the first electrode.

The electron hits the first electrode and causes the release of several electrons. Figure 9 shows how a series of accelerations and collisions produces a large number of electrons. These electrons hit the anode and produce a pulse of current in an ammeter.

Figure 10 shows the variation of current in the ammeter with time due to this pulse.

Determine the number of electrons that flow through the ammeter.

Which row shows SI unit prefixes in order of smallest value to largest value?

Which diagram represents electron capture?

Which decay of a positive kaon (K +) particle is possible?

The diagram shows four energy levels of an atom drawn to scale. These energy levels give rise to part of an emission spectrum.

Which pattern of lines will be observed from these energy levels?

What is the de Broglie wavelength when the particle has a kinetic energy of 4E_k?

A wave travels along a water surface.

The variation with time of the displacement of a water particle at the surface is shown.

What properties of the wave are represented by w and z ?

Two points on a progressive wave are out of phase by 0.41 rad.

What is this phase difference?

Which row gives another arrangement that produces a fringe spacing of w ?

A narrow beam of monochromatic light is incident normally to a diffraction grating. The first-order diffracted beam makes an angle of 20° with the normal to the grating.

What is the highest order visible with this grating at this wavelength?

The speed of light decreases by 40% when it travels from air into a transparent medium.

What is the refractive index of the medium?

Which row describes charge and impulse?

An object is in equilibrium when acted on by three coplanar forces.

Which free-body diagram is correct?

Each diagram is drawn to scale.

Which quantity is represented by the area under a force–time graph?

Each diagram shows two horizontal forces acting on a solid square object seen from above.

All the forces have the same magnitude.

Which system produces a couple about any point inside the object?

A uniform metre ruler of weight 2.0 N is freely pivoted at the 70 cm mark.

A student holds the ruler in a horizontal position and suspends a 5.0 N weight from the 100 cm end.

What is the magnitude of the resultant moment when the student releases the ruler?

The diagram shows how the speed v of an object varies with time t.

Which graph shows the variation of distance s with t for the object?

Two ball bearings X and Y are projected from horizontal ground at the same time.

X has mass 2 m and is projected vertically upwards with speed u.

Y has mass m and is projected at 30 to the horizontal with speed 2u.

Air resistance is negligible.

Which statement is correct?

Which row is true for an elastic collision between two objects in an isolated system?

The drag force on a boat is kv², where v is the speed and k = 64 kg m¹.

The boat’s engine has a useful power output of 8000 W.

What is the maximum speed of the boat?

A tensile force F₁ causes a wire to stretch to length x₁.

When the tensile force is increased to F₂ the length of the wire is x₂.

The wire obeys Hooke’s Law.

What is the additional energy stored in the wire as the length increases from x₁to x₂?

Which is a force–extension graph for a brittle material?

The table shows corresponding values of potential difference V and current I for four electrical components A, B, C and D.

Which component is an ohmic conductor with the greatest resistance?

Which row shows the resistances of an ideal ammeter and an ideal voltmeter?

The capacity of a portable charger is rated in ampere hours (A h). A charger of capacity 1 A h can provide 1 A for 1 hour at its working voltage.

One charger has a capacity of 1800 mA h at a working voltage of 3.7 V.

What is the energy stored in this charger?

A filament lamp with resistance 12 Ω is operated at a power of 36 W.

How much charge flows through the filament lamp during 15 minutes?

What is the diameter of the wire?

The potential difference between points X and Y is V.

What is the potential difference between P and Q ?

The diagram shows a temperature-sensing circuit.

The temperature of the thermistor is decreased.

Which row shows the changes to the ammeter reading and the voltmeter reading?