OCR A Level Physics A Exploring Physics June 2018 question paper H556/02

Which electrical quantity has S.I. units ampere-second (A s)?

A charge

B current

C resistance

D potential difference

Your answer

A vibrating tuning fork is held above the open end of a long vertical tube. The other end of the tube, which is also open, is immersed in a tank of water. The length L of the air column within the tube is changed by raising or lowering the tube.

The wavelength of sound from the vibrating tuning fork is 150.0 cm.

What length L of air column will not produce a stationary wave within the tube?

A 37.5 cm

B 75.0 cm

C 112.5 cm

D 187.5 cm

Your answer

Which is the best value for the elementary charge e in terms of both accuracy and precision?

Your answer

A small loudspeaker emits sound uniformly in all directions. The amplitude of the sound is 12 m at a distance of 1.5 m from the loudspeaker.

What is the amplitude of the sound at a distance of 4.5 m from the loudspeaker?

A 1.3 m

B 4.0 m

C 6.9 m

D 12 m

Your answer

An isolated metal sphere is charged using a power supply.

Which single quantity can be used to determine the capacitance of the sphere?

A The diameter of the sphere.

B The charge on the sphere.

C The resistance of the metal.

D The e.m.f. of the power supply.

Your answer

A capacitor is charged through a resistor.

The cell has e.m.f. 1.50 V and negligible internal resistance. The capacitor is initially uncharged. The time constant of the circuit is 100 s. The switch is closed at time t = 0.

What is the potential difference across the capacitor at time t = 200 s?

A 0.20 V

B 0.55 V

C 0.95 V

D 1.30 V

Your answer

A charged particle moves in a circular path of radius 1.2 cm in a uniform magnetic field.

The direction of the magnetic field is perpendicular to the plane of the paper.

The particle has mass m, charge + Q and speed v.

Another particle of mass 3 m, charge +2 Q and speed v moves in a circular path of radius R in the same magnetic field.

What is the value of R ?

A 0.8 cm

B 1.2 cm

C 1.8 cm

D 7.2 cm

Your answer

The acoustic impedance Z of a material in the shape of a cube can be determined using the equation

where M is the mass of the material, L is the length of each side of the cube and c is the speed of ultrasound in the material.

The percentage uncertainty in L is 1.2 % and the percentage uncertainty in c is 1.8 %. The percentage uncertainty in M is negligible.

What is the percentage uncertainty in Z ?

A 2.2 %

B 3.0 %

C 4.2 %

D 5.4 %

Your answer

The table shows some data on two tissues in a patient.

Tissue	Density	Acoustic impedance
X		1.5 Z
Y	1.3	Z

Ultrasound in tissue X is incident at the boundary between the tissues X and Y.

What is the percentage of the ultrasound intensity reflected at the boundary?

A 1.7 %

B 4.0 %

C 13 %

D 20 %

Your answer

An electron is released at a distance r from the surface of a positively charged sphere. It is attracted towards the centre of the sphere and moves until it touches the surface.

Which of the following statements is/are correct?

1 The area under the F against r graph is equal to work done on the electron.

A Only 1

B Only 1 and 2

C Only 1 and 3

D 1, 2 and 3

Your answer

Which lepton is emitted in the decay of an up quark and is affected by a magnetic field?

A neutrino

B electron

C positron

D antineutrino

Your answer

A contrast material is used while taking an X-ray image of a patient.

Which statement is correct?

A Iodine is a contrast material.

B Technetium is a contrast material.

C A contrast material must have a short half-life.

D A contrast material is used for acoustic matching.

Your answer

Derive the S.I. base units for resistance.

Fig. 16.1 shows the I-V characteristics of two electrical components L and R.

The component L is a filament lamp and the component R is a resistor.

Show that the resistance of R is 40 .

17* A metal circular plate is rotated at a constant frequency by an electric motor. The plate has a small hole close to its rim. Fig. 17.1 shows an arrangement used by a student to determine the frequency of the rotating

A light-dependent resistor (LDR) and a fixed resistor of resistance 1.2 k are connected in series to a battery. The battery has e.m.f. 4.5 V and has negligible internal resistance. The potential difference V across the resistor is monitored using a data-logger.

Fig. 17.2 shows the variation of V with time t.

Use your knowledge and understanding of potential divider circuits to explain the shape of the graph shown in Fig. 17.2. Include in your answer the maximum and minimum values of the resistance of the LDR. Describe how the student can determine the frequency of the rotating plate.

A narrow beam of unpolarised light is incident at the boundary between air and glass.

Fig. 18 shows the incident ray, the reflected ray and the refracted ray at the air-glass boundary.

The refractive index of air is 1.00 and the refractive index of the glass is 1.50. The angle of incidence of the light is 56.3°.

Show that the angle between the refracted ray in the glass and the reflected ray in the air is 90.0°.

Describe how you can demonstrate in the laboratory that the reflected light is plane polarised.

Calculate the time t taken for the refracted light to travel a depth of 6.0 cm of glass.

Fig. 19.1 shows the image from an experiment using a ripple tank.

A straight ruler repeatedly hits the surface of water. Waves on the surface of the water travel in the direction shown by the two large upward white arrows. The waves are incident at a solid barrier.

Closely examine the image shown in Fig. 19.1.

State two wave phenomena (properties) that can be observed in this image. You may annotate Fig. 19.1 to support your answer.

Draw the straight line of best fit on Fig 20.1 and determine the gradient of the line.

gradient =........ V m

Calculate the percentage difference between your value in (ii) and the accepted value of the Planck constant.

Identify the two types of errors shown by the data in Fig. 20.1 and suggest how you could have refined the experiment to reduce or eliminate these errors.

Fig. 20.2 shows a gold-leaf electroscope with a clean zinc plate.

The zinc plate, metal stem and the gold-leaf are given a negative charge by briefly connecting the zinc plate to the negative electrode of a high-voltage supply.

The gold leaf is fully diverged.

The position of the leaf is not affected by intense white light from a table lamp incident on the zinc plate. The gold leaf collapses very quickly when low-intensity ultraviolet radiation from a mercury lamp is incident on the zinc plate.

Explain these observations in terms of photons.

Fig. 21.1 shows a coil of a simple generator rotating in a uniform magnetic field.

The coil has 85 turns of insulated wire. The cross-sectional area of the coil is 14 cm². Fig. 21.2 shows the variation of magnetic flux density B through the plane of the coil with time it rotates.

Explain why the electromotive force (e.m.f.) induced across the ends of the coil is a maximum at the times when B = 0.

Draw a tangent to the curve in Fig. 21.2 when B = 0, and hence determine the maximum e.m.f. induced across the ends of the coil.

maximum e.m.f. =........ V

Fig. 21.3 shows the variation of the e.m.f. induced across the ends of the coil with time t.

The magnitude of the magnetic flux density of the uniform field is now halved and the coil is rotated at twice its previous frequency.

On Fig. 21.3 sketch the new variation of the e.m.f. induced with time t.

A student wishes to determine the permittivity of paper using a capacitor made in the laboratory.

The capacitor consists of two large parallel aluminium plates separated by a very thin sheet of paper.

The capacitor is initially charged to a potential difference V₀ using a battery. The capacitor is then discharged through a fixed resistor of resistance 1.0 M.

The potential difference V across the capacitor after a time t is recorded by a data-logger. The student uses the data to draw the ln V against t graph shown in Fig. 22.

Show that the magnitude of the gradient of the line shown in Fig. 22 is equal to

where C is the capacitance of the capacitor and R is the resistance of the resistor.

* Use Fig. 22 to determine the capacitance C of the capacitor. Describe how the student can then use this value of C to determine a value for . In your description, mention any additional measurements required on the capacitor.

The structure of atoms was deduced in the early 1900s by Rutherford and his co-workers from the scattering of alpha-particles by a very thin sheet of gold.

Rutherford assumed that the scattering of the alpha-particles was due to electrostatic forces. Fig. 23 shows a detector used to record the number N of alpha-particles scattered through an

At = 0°, N was too large to be measured. The table below summarises some of the collected data.

/ °	lg (N)
150	1.5
75	2.3
60	2.7
30	3.9
15	5.1
0	N too large

Show that the number of alpha-particles scattered through 15° is about 4000 times more than those scattered through 150°.

Use the evidence from the table to explain the structure of the atom.

A proton with kinetic energy 0.52 MeV is travelling directly towards a stationary nucleus of cobalt-59 (⁵⁹₂₇Co) in a head-on collision.

Explain what happens to the electric potential energy of the proton-nucleus system.

Calculate the minimum distance R between the proton and cobalt nucleus.

An isotope of polonium-213 (²¹³₈₄Po) first decays into an isotope of lead-209 (²⁰⁹₈₂Pb) and this lead isotope then decays into the stable isotope of bismuth (Bi).

Fig. 24 shows two arrows on a neutron number N against proton number Z chart to illustrate these two decays.

Complete the nuclear decay equations for

the polonium isotope

the lead isotope.

A pure sample of polonium-213 is being produced in a research laboratory. The half-life of²¹³₈₄Po is very small compared with the half-life of²⁰⁹₈₂Pb.

After a very short time, the ionising radiation detected from the sample is mainly from the beta-minus decay of the lead-209 nuclei.

Briefly describe and explain an experiment that can be carried out to confirm the beta-minus radiation emitted from the lead nuclei.

The activity of the sample of²⁰⁹₈₂Pb after 7.0 hours is 12 kBq. The half-life of²⁰⁹₈₂Pb is 3.3 hours.

Calculate the initial number of lead-209 nuclei in this sample.

Explain why a high-speed proton is necessary to trigger the nuclear reaction shown above.

Estimate the minimum wavelength λ of the gamma ray photon ().

Fluorine-18 is a positron emitter. Name a medical imaging technique that uses fluorine-18 and state one benefit of the technique.

Describe how the components of a computerised axial tomography (CAT) scanner can produce high-quality images of the internal structures of a patient.