SECTION A (25 marks)
Answer all the questions in this section in the spaces provided.
- Figure 1 shows two parallel rays from a distant object passing through a convex lens:

- Indicate on the diagram, the position of the principal focus on the lens. (1 mark)
- Deremine the focal length of the lens. (1 mark)
- State the effect of decreasing the distance between the plates of the parallel plate capacitor on the capacitance. (1 mark)
- Figure 2 shows circular waves originating from the principal focus F of a concave mirror and moving towards the mirror.

Complete the diagram to show the refflected waves. (1 mark)
- The force of an electromagnetic wave is 4.0 x 106 Hz. Determine its wavelength. (take speed of light as 3.0 x 108 ms-1) (3 marks)
- Figure 3 shows a nail on which a wire is to be wound to make an electromagnet.

By drawing, show how the wire should be wound around the nail so that end A becomes a north pole and B becones a south pole. (1 mark)
- It is observed that when the cap of an uncharged electroscope is irradiated with light of high frequency, the leaf of the electroscope rises. Explain this observation. (3 marks)
- Figure 4 shows the magnetic field pattern around two bar magnets placed side by side.

Indicate on the diagram the poles of each magnet. (1 mark)
- Figure 5 shows a graph ofcurrent against voltage for a semiconductor diode.

In the space provided, draw a circuit diagram that may be used to obtain values needed to draw the graph in figure 5. (3 marks)
- Radium undergoes radioactive decay by emiting an alpha particle to form a daughter nuclide Q as in the reaction:

Determine the values of:- x (1 mark)
- y (1 mark)
- State two uses of a charged gold leaf electroscope. (2 marks)
- The anode of an x-ray tube becomes hot when the tube is in use. State the reason for this. (1 mark)
- Draw a ray diagram to show how a ray of light may be totally internally reflected two timesin an isosceles right anlgled glass prism. (Assume that the critical angle of glass is 420) (2 marks)
- The current of electrons hitting the screen of a cathode ray oscilloscope is 2.0 x 10-4 A.
Determine the number of electrons that strike the screen each second. (take charge of an electron as 1.6 x 10-19 C)
SECTION B (55 marks)
Answer all the questions in this section in the spaces provided.
- Figure 6 shows a simple electric bell circuit.

- Name the parts labelled:
- D (1 mark)
- E (1 mark)
- When the switch is closed, the hammer hits the gong repeatedly. Explain why:
- The hammer hits the gong. (2 marks)
- The hammer hits the gong repeatedly. (3 marks)
- An electric bulb is rated 60 W, 240 V. Determine:
- the current that flows through it when it connected to 240 V supply. (3 marks)
- the resistance of the bulb. (3 marks)
- One of the causes of energy loss in a transformer is heating in the coils when current flows. State:
- The reason why the current causes heating. (1 mark)
- How the heating can be minimized. (1 mark)
- The input voltage of a transformer is 240 V and its output is 12 V. When an 80 W bulb is connected across the secondary coil, the current in the primary coil is 0.36 A.
Determine:- The ratio Np/Ns of the transformer, (where Np is the number of turns in the primary coil and Ns is the number of turns in the secondary coil) (3 marks)
- The power input of the transformer. (3 marks)
- The power output of the transformer. (1 mark)
- The efficiency of the transformer. (2 marks)
- Figure 7 shows resistors R1 and R2 connected in parallel. Their ends are connected to a battery of potential difference V volts.

- In terms of V1,R1 and R2, write an expression for:
- Current I1 through R1. (1 mark)
- Current I2 through R2 . (1 mark)
- Total current I in the circuit. (1 mark)
- Show that the total resistance RT is given by
(3 marks)
- Figure 8 shows a negatively charged rod placed near an uncharged conductor resting on an insulating support.

- Show the charge distribution on the conductor. (2 marks)
- State the effect:
- Of momentarily touching the conductor with a finger while the charged rod is still near the conductor. (1 mark)
- On the charge distribution of withdrawing the negatively charged rod after momentarily touching the conductor. (1 mark)
- In the space provided, sketch a diagram to show how the charge in (ii) (II) above would have been distributed if the conductor was a sphere. (1 mark)
- Figure 9 shows two speakers S1 and S2 which produce sound of the same frequency. They are placed equidistant from a line AB and a line PQ. (PQ is perpendicular to line AB)

- A student walking from A to B hears alternating loud and soft sounds. Explain why at some point the sound heard is soft. (2 marks)
- The student now walks along line PQ. State the reason the nature of the sound the student hears. (3 marks)
- Figure 10 shows sound waves in air produced by a vibrating tuning fork. R is an air molecule on the path of the waves.

- Using a line, indicate on the diagram a distance d equal to the wavelength of the wave. (1 mark)
- In the space provided, show with an arrow the direction of motion of the air molecule fr as the waves pass. (1 mark)
- Explain the reason for the answer in (ii). (2 marks)
- Figure 11 shows an object placed 10cm infront of a concave mirror whose radius is of curvature is 40 cm.

- On the same figure, draw a diagram to show the position of the image formed. (3 marks)
- Use the ray diagram to determine:
- the image distance. (1 mark)
- the magnification. (3 marks)
- State where the position of the image would be if the object had been placed at the principal focus. (1 mark)
- Draw a ray diagram to show the formation of a partially dark shadow and a totally dark shadow during the eclipse of the sun. (3 marks)