### SECTION A: (25 Marks)

Answer all questions in this section in the spaces provided
1.

State two conditions under which a pinhole camera may form an image on its screen which has the same size as the object. .................................................................................................................................................................. .................................................................................................................................................................. ..................................................................................................................................................................

2 marks

2.

Figure 1 shows a ray of light incident along the normal. The mirror is rotated at an angle of 150 in a clockwise direction without changing the position of the incident ray,

Determine the angle between the reflected ray and the incident ray. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. ..................................................................................................................................................................

2 marks

3.

A steel nail is to be magnetized by the electrical method as shown in figure 2. Identify the poles P and Q of the resulting magnet.

P: .............................................................................................................................................................. Q:..............................................................................................................................................................

1 marks

4.

State the purpose of cooling fins in the X-ray tube. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. ..................................................................................................................................................................

1 marks

5.

The figure 3 shows two waveforms representing the same wave motion

Determine the velocity of the wave. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. ..................................................................................................................................................................

3 marks

6.

An object O is placed in front of a concave mirror and on the principal axis, as shown in the figure 4. Complete the light ray diagram to locate the position of the image.

3 marks

7.

A house has a lighting circuit operated from a 240V mains supply. Four bulbs rated 40W 240V and six bulbs rated 100W 240V are switched on for 5 hours a day. Determine the monthly bill for the consumer given that the cost of electricity is at Kshs. 5.50 per unit. (Take 1 month =30 days and the standing charge is sh.150)

.................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. ..................................................................................................................................................................

3 marks

8.

A charge conductor is slowly brought near the cap of a positively charged electroscope. The leaf first collapse and then diverges. State the charge on the conductor.

..................................................................................................................................................................

1 marks

9.

A girl standing at a distance claps her hands and hears an echo from a tall building 2 seconds later. If the speed of sound in air is 340m/s, determine how far the building is.

.................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. ..................................................................................................................................................................

3 marks

10.

A current â€“ carrying conductor AB is in a magnetic field as shown in the figure 5.

a) Indicate the direction of force F acting on the conductor. (1mk)

b) State two factors that determine the direction of the force F. (2mks) ...................................................................................................................................................... ......................................................................................................................................................

3 marks

11.

You are given three resistors of values 5Î©, 8Î© and 12Î©. Show in a circuit diagram how you would connect them so as to give:

a) An effective resistance of 9.8Î© (2mks)

b) The least effective resistance. (1mk)

3 marks

### SECTION B: (55 Marks)

Answer all the questions in this section in the spaces provided.
12.

a) Define refractive index (1mk)

...................................................................................................................................................... ......................................................................................................................................................

b) The critical angle of a certain material medium is 43.20. Determine the refractive index of the material. (2mks) ...................................................................................................................................................... ...................................................................................................................................................... ...................................................................................................................................................... ......................................................................................................................................................

c) A small bright object O lies at the bottom of a beaker containing water depth h cm. A convex lens of focal length 15cm is held at the surface of water. The lens forms an image of O at 45cm from the surface of water, as shown in the figure below.

Taking the refractive index of water to be 4/3, determine: i) the apparent depth of the object (2mks) ...................................................................................................................................................... ...................................................................................................................................................... ...................................................................................................................................................... ......................................................................................................................................................

ii) the real depth h, of the object (2mks)

...................................................................................................................................................... ...................................................................................................................................................... ...................................................................................................................................................... ......................................................................................................................................................

d) i) What do you understand by the term accommodation? (1mk) ...................................................................................................................................................... ......................................................................................................................................................
ii) The diagram in figure 6 shows a certain defect of vision.

Name the defect (1mk) ...................................................................................................................................................... ......................................................................................................................................................

iii) On figure 7 below show how the defect can be corrected. (2mks)

e) An object is placed 40cm in front of a concave lens of focal length 20cm; determine the position of the image. (3mks) ...................................................................................................................................................... ...................................................................................................................................................... ...................................................................................................................................................... ...................................................................................................................................................... ......................................................................................................................................................

14 marks

13.

a) State what is meant by the term capacitance. (1mk) ...................................................................................................................................................... ......................................................................................................................................................

b) David was asked to distinguish between a paper capacitor and an electrolyte capacitor. In your opinion, what was his response? (1mk) ...................................................................................................................................................... ...................................................................................................................................................... ......................................................................................................................................................

c) Figure 8 below shows a network of capacitance in series

i) Derive an expression for their effective capacitance CE from first principles. (4mks) ................................................................................................................................................. ................................................................................................................................................. ................................................................................................................................................. .................................................................................................................................................

ii) Given that C1=10.5Î¼F, C2=2Î¼F and C3=3Î¼F. Calculate CE in (2) above and hence determine the charge stored on each capacitor. (4mks) ................................................................................................................................................. ................................................................................................................................................. ................................................................................................................................................. .................................................................................................................................................

d) Capacitors have a wide range of applications. Briefly describe their in rectification.(1mk) ................................................................................................................................................. ................................................................................................................................................. ................................................................................................................................................. .................................................................................................................................................

11 marks

14.

. a) Figure 9 is a signal displayed on the Y- plate of a C.R.O. If the sensitivity of the Y- gain is 200V/cm and the time base control is set at 40ms/cm

Calculate; i) The peak voltage of the signal. (2mks)
ii) The frequency of the signal. (3mks)

b) How would you increase the density of X-rays in an X-ray tube? (1mk) ...................................................................................................................................................... ......................................................................................................................................................

c) An X-ray tube operates at cathode current of 40mA. Calculate the number of electrons striking the target metal per second. (Take the charge of an electron as 1.6 X 10-19C.) (3mks) ...................................................................................................................................................... ...................................................................................................................................................... ...................................................................................................................................................... ......................................................................................................................................................

9 marks

15.

The figure below shows a connection to the three pin plug.

i) Identify the mistakes in this wiring. (3mks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

ii) What would happen if this plug was connected to the mains of the socket? (1mk) .............................................................................................................................................

.............................................................................................................................................

iii) State two reasons why the earth pin is normally longer than the other two pins. (2mks) ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

b) A house has five rooms with 240V, 60W bulbs. If the bulbs are switched on from 7.00p.m. to 10.30p.m.

i) Calculate the power consumed per day in Kilowatt â€“hours (3mks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

ii) Find the cost per week for lighting these rooms at Kshs.6.70 per unit. (3mks) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

12 marks

16.

a) Distinguish between transverse and longitudinal waves. (1mk) ............................................................................................................................................. .............................................................................................................................................

b) The figure below shows an arrangement used to observe interference pattern of red light.

S1 and S2 are slits; B is a source of light, images or fringes that are formed on the screen.

State what happens to the separation of fringes when; i) Slit separation is increased (1mk) .............................................................................................................................................
.............................................................................................................................................
ii) Green light is used (1mk)

............................................................................................................................................. .............................................................................................................................................

iii) State with a reason (s) what is observed on the screen when green light is used (3mks) ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

c) State what is observed on the screen when monochromatic white light is used. (3mks) ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................

9 marks

Back Top