OCR GCE AS Level Physics A AS Paper 2 November 2020 question paper H156/02

A sound wave is an example of a longitudinal wave.

State what is meant by the term longitudinal wave.

A microphone is connected to an oscilloscope. Sound of frequency 500 Hz is incident on the microphone. The oscilloscope time-base is set to 0.5 ms cm⁻¹ and the y-gain set to 1.0 mV cm⁻¹. The signal displayed on the oscilloscope screen has an amplitude of 2.0 mV. The oscilloscope grid is shown below.

Sketch the oscilloscope trace on the grid above.

Microwaves and X-rays are examples of electromagnetic waves.

The following are possible wavelengths of electromagnetic waves.

0.2 km 2 m 2 cm 0.2 mm 2 m 200 nm 200 pm

Select from the list above a typical wavelength of a microwave and an X-ray.

microwave........

X-ray........

One property of electromagnetic waves is that they are transverse waves.

State two other properties.

The table shows the refractive index n of air and glass for blue light. It also shows the speed v and the wavelength of blue light in air.

	air	glass
refractive index n	1.00	1.53
speed of light v / m s−1	3.00 × 108
wavelength / m	4.69 × 10−7

Show that the frequency f of blue light in air is 6.40 × 10¹⁴ Hz. (i)

Complete the table by determining the missing values for v and for glass. Write your answers to 3 significant figures.

A semi-circular block of glass is placed in air. Fig. 2.1 shows the path of blue light through the air and the semi-circular glass block.

The angle i is 30°.

1. Determine angle p.

2. Determine angle q, using the information from the table in (a).

The angle i is increased from 30° to 60°. Describe and explain how angles p and q will change. In your answer, include the term critical angle.

Fig. 2.2 shows the same semi-circular glass block with the blue light replaced by red light.

The dashed lines show the original paths of the blue light.

Draw on Fig. 2.2 the path of the red light in the glass block and out of the glass block.

Show that the gradient of the straight line of best fit is about 0.12 m kg⁻¹.

Using the gradient, determine a value for k. Give your answer to an appropriate number of significant figures and include an appropriate unit.

Draw a worst acceptable straight line.

Determine the gradient of your worst acceptable line.

gradient of worst acceptable line =........ m kg⁻¹

Determine the percentage uncertainty in k.

4* A metal ball leaves a horizontal surface with velocity v. A student investigates the horizontal distance R that the ball travels before it hits the ground.

It is suggested that the relationship between R and v is given by

where g is the acceleration of free fall and Q is a constant.

Describe with the aid of a suitable diagram how an experiment can be safely conducted, and how

the data can be analysed, to determine Q.

A car is travelling at a constant speed of 20 m s⁻¹ along a straight road. The driver sees a hazard ahead in the road, applies the brakes and brings the car to a stop. The graph below shows the displacement s against time t for the car from the time that the driver sees the hazard to when the car stops.

The braking force F acting on the car is constant. The mass of the car is 950 kg. The reaction time of the driver is 0.75 s.

State the gradient of the graph when t = 0.

gradient =........ m s⁻¹

Explain how you can deduce from the graph that the brakes are applied at time t = 0.75 s.

Draw a tangent to the graph at time t = 1.75 s. Use this tangent to show that the speed of the car at t = 1.75 s is about 12 m s⁻¹.

Determine the braking force F. You may use information from (c) or from the graph.

Describe and explain the variation of the displacement with time when the same driver applies the brakes in the same car when the initial speed of the car is 10 m s⁻¹.

Fig. 6.1 shows a uniform metal cylinder of weight 7.0 N. The cylinder has length 100 mm and diameter 32 mm.

Fig. 6.1 (not to scale)

Calculate the density of the metal.

=........ kg m⁻³

The cylinder is suspended by two cords A and B, attached to the centre of the top surface, as shown in Fig. 6.2.

The tensions in each of the cords are T_A and T_B.

Fig. 6.3 shows T_B drawn to scale on graph paper.

Scale 1.0 cm represents 2.0 N.

Determine the magnitude of T_B.

Draw a triangle of forces on Fig. 6.3 to represent the forces acting on the cylinder. Determine the magnitude of T_A.

Determine the angle in Fig. 6.2.

Fig. 6.4 shows the same cylinder at rest on a bench. A horizontal force F is applied to the cylinder so that it can rotate about point X.

Calculate the minimum value of F to just topple the cylinder about X.

A 150 W heater constructed from nichrome wire is switched on for 5.0 hours.

The wire has a cross-sectional area of 4.1 × 10⁻⁹ m². The current in the wire is 1.5 A. The number density of charge carriers in nichrome is 7.9 × 10²⁸ m⁻³.

Calculate

the resistance R of the heater

the number N of electrons passing through the heater in 5.0 hours

the mean drift velocity v of the electrons (charge carriers) in the heater.

v =........ m s⁻¹

The cost of 1 kWh of energy is 16p. Calculate the cost of using the heater for 5.0 hours.

8* A student is investigating electron diffraction. A beam of electrons is directed towards a thin slice of graphite in an evacuated tube. The electrons are accelerated by a potential difference of 2000 V. The diagram below shows the pattern formed on the fluorescent screen of the evacuated tube.

Describe and explain how the pattern changes as the potential difference is increased. Include

how the de Broglie wavelength of the electron is related to the potential difference V.