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Form 4 Physics Paper 2 Question Paper

Form 4 Physics Paper 2

Course:Physics

Exam Year:2007

SECTION A (25 MARKS)
Answer all the questions in this section in the spaces provided
1. Figure 1 represents a pinhole camera

Sketch rays to show the formation of an enlarged image in the camera. Label both the object and the image (2 marks)
2. State one advantage of an alkaline cell over a lead – acid cell (1 mark)
3. Figure 2 shows a horse – shoe magnet whose poles are labeled and two other magnets near it.
Iron are attracted to the lower ends of the n\magnets as shown.

Identify the poles marked X and Y (1 mark)
X …………………………………….Y………………………………………
4. Figure 3 shows an object, O in front of a concave mirror and its image, I formed after reflection.

(a) On the same diagram draw appropriate ray (s) to locate the principal focus, F, of the mirror. (2 marks)
(b) Determine the focal length of the mirror (scale 1: 5) (1 mark)
5. Figure 4. shows the displacement – time graph for a certain wave

Determine the frequency of the wave (3 marks)

6. Figure 5 (a) and (b), show wavefronts incident on barriers blocking part of the path.

On the same figures sketch the wavefronts to show the behavior of the waves as they pass each barrier and after passing the barrier. (1 mark)

7. Figure 6 shows a ray of light incident on the face of a water prism

Sketch the path of the ray as it passes though the prism
Critical angle for water is 490 (1 mark)

8. In the circuit diagram shown in figure 7, the ammeter has negligible resistance
When the switch S, is closed, the ammeter reads 0.13 A.

Determine the internal resistance of the cell ( 3 marks)
9. A heater of resistance R1 is rated P watts, V volts while another of resistance R2 is rated 2P watts, V/2 volts. Determine R1 / R2 (3 marks)

10. State what is meant by the term accommodation as applied to the human eye.
(1 mark)

11. The graph in figure 8 shows the variation of photoelectric current with applied voltage when a surface was illuminated with light of a certain frequency. Use the information in the figure to answer questions 11 and 12.

On the same axes, sketch the graph when light of higher intensity but same frequency is used to illuminate the surface. (1 mark)

12. Explain your answer in 11 above (1 mark)

13. The following is part of radioactive decay series

234 a 230
Bi ß X Y

83 84 b

Determine the values of a and b (2 marks)
a = ……………………………………. b= …………………………………

14. You are provided with a diode, a resistor R, an a.c source of low voltage and connecting wires.
In the space provided, sketch the circuit diagram for a half – wave rectifier and indicate the terminals where the output voltage V0 may be connected. (2mks)

SECTION B (55 MARKS)
Answers ALL the questions in this section in the spaces provided.
15. (a) State Ohm’s Law ( 1 mark)

(b) The graph in figure 9 shows the current – voltage characteristics of a certain device, X

(i) State with a reason whether the device obeys Ohm’s law (2 marks)
(ii) Determine the resistance of the device, X, when the current through it is
60 mA.
(iii) When the device, X is connected in the circuit below, the voltage across it
is 0.70 V.

Calculate the value of the resistance R. (3 marks)

(c) The cell in figure 10 has an e.m.f of 2.1 V and negligible internal resistance.

Determine the
(i) Total resistance in the circuit (2 marks)
(ii) Current in the circuit (1 mark)
(iii) Reading of the voltmeter (2 marks)

16. (a) Figures 11 (a) and (b) show diagrams of the human eye

(i) Sketch in figure 11 (a) a ray diagram to show shortsightedness (1 mark)
(ii) Sketch in figure 11 ( b) a ray diagram to show how a lens can be used to
correct the shortsightedness (2 marks)

(b) Figure 12 shows the features of a simple camera

(i) Name the parts labeled A and B (2 marks)
A ………………………………………..
B ……………………………………….
(ii) A still object is placed at a certain distance from the camera. Explain the adjustments necessary for a clear image of the object to be formed.
(iii) State the functions of the shutter and the parts labeled A and B (3 marks)
Shutter ………………………………………………………………….
A…………………………………………………………………………
B ………………………………………………………………………..

(c) A lens forms a clear image on a screen when the distance between the screen and the object is 80cm. If the image is 3 times the height of the object, determine.
(i) The distance of the image from the lens (3 marks)
(ii) The focal length of the lens (2 marks)

17. (a) State Lenz’s Law of electromagnetic induction (1 mark)
(b) Figure 13 shows a simple microphone in which sound waves from the person talking cause the cardboard diaphragm to vibrate

(i) Explain how a varying current is induced in the coil when the diaphragm vibrates (3 marks)
(ii) State two ways in which the induced current in (i) above can be increased
(c) A transformer with 1200 turns in the primary circuit and 120 turns in the secondary circuit has its primary circuit connected to a 400V a.c source. It is found that when a heater is connected to the secondary circuit, it produces heat at the rate of 600w. Assuming 100% efficiency, determine the:
(i) Voltage in the secondary circuit (2 marks)
(ii) Current in the primary circuit (2 marks)
(iii) The current in the secondary circuit (1 mark)

18. (a) Figure 14 shows the features of a cathode ray tube

(i) Name the parts labeled A and B (2mks)
A …………………………………. B…………………………….
(ii) Explain how the electrons are produced in the tube (2 marks)
(iii) State two functions of the anodes (2 marks)
(iv) At what part of the cathode ray tube would the time be connected?
(v) Why is a vacuum created in the tube? (1 mark)

(b) The graph in figure 15 was obtained on a cathode ray oscilloscope (CRO) screen when the output of an a.c generator was connected to the input of the CRO. The time- base calibration of the CRO was set at 20 milliseconds per centimeter and the y- gain at 5 volts centimeter.

(i) Determine the pick voltage of the generator (2mks)
(ii) Determine the frequency of the voltage (3 marks)
On the same grid, redraw the graph for the same voltage when the time base calibration is set at 40 milliseconds per centimeter and y- gain at 10 volts per centimeter. (Show at least one complete cycle) (2 marks)

Form 4 Physics Paper 2 Question Paper

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