The figure below shows a ray of light incident on a glass prism.

Given that the critical angle for the glass is 390, sketch on the diagram the path of the ray through the prism.

a) Machines at a textile industry experiences electrostatic forces at certain points. Suggest a method that can be used to reduce these forces. (1marks)
(b) A sharp point of a pin is held over a positively charged electroscope. State and explain the observation made on theelectroscope. (2mks)

State two ways in which energy is lost in a transformer and how it can be minimized in each case.

An echo sounder produces a pulse and an echo is received from the sea bed after 0.4 seconds. If the speed of sound in water is 1500m/s. Calculate the depth of the sea bed.

Sketch the magnetic field pattern of the following arrangement.

State what is meant by extrinsic semiconductor.

The graph below shows the displacement of a pendulum bob from its rest position as it varies with time.

What is the frequency of the pendulum?

State one use and one source of gamma rays.
Use:________________________________________________________________
Source:_____________________________________________________________

A thermistor, TH, is connected in parallel with a bulb as shown in figure below. The bulb is lit. When the thermistor is steadily heated the brightness of the bulb reduces explain this observation.

The initial mass of a radioactive substance is 40g. The substance has a half-life of 10 years. Determine the mass remaining after 40 years.

A wire of resistance 27 ohms is cut into three equal lengths. If the three wires are connected in parallel, what is the effective resistance?

What is local action in a dry cell and how is it minimized?

State the Flemings right –hand rule for a straight conductor carrying current

1n an experiment to find the relationship between frequency of radiation and kinetic energy of photoelectrons in a photoelectric device, the following graph was obtained.

Use the graph to answer the following questions,
a) i) Determine the threshold frequency. (1 mark)
ii) Find the plank's constant h. .(Take the charge of an electron to be 1.6 x 10-19 C) (2 marks)
iii) Calculate the work function of the metal in joules. (2 marks)
b) Calculate the photon energy in ultraviolet radiation whose frequency is 8.60 x 1014 Hz. (Plank’s constant h=6.63 x 10-34 Js)
(2mks)
c) The figure below shows a bridge rectifier.

i) Define the term rectification. (1 mark)
ii) Describe how the illustrated rectifier works. (2 marks)
iii) State the modification that can be made on the arrangement to improve the quality of the output. (1 mark)

iv) Sketch on the areas below how the improved output is displayed on a C.R.O screen. (1 mark)

(a) A transformer has 800 turns in the primary windings. The alternating e.m.f connected to the primary is 240V and the current flowing is 0.2A. Find the power in the secondary coil if the transformer is 90% efficient (3marks)
(b) The figure below shows a domestic wiring system.

(i) Point out two faults in the circuit. (2marks)
(ii) What is the fuse made of and why is it necessary in the circuit? (2marks)
(c) State 2 ways of minimizing power loss in transmission lines. (2marks)
(d) The figure below shows a simple generator and the arrows indicate the direction of induced current.

(i) What type of generator is shown above ? (1mark)
(ii) State two ways of increasing the brightness of the bulb. (2marks)
(iii) If the bulb was replaced by a CRO sketch on the axes provided a graph to show the variation of
output emf with position of the coil starting from vertical position. (2marks)

a) i) Ra decays into Rn by emission of an alpha particle. Write a nuclear equation for the decay
(2marks)
ii) What do you understand by the term half-life of a radioactive substance. (1mark)
b) The figure below shows a G.M tube.

i) What is the purpose of the mica window? (1mark)
ii) What is the purpose of the bromine (1mark)
iii) Briefly explain how it works. (2marks)

(a) Figure below shows a pair of parallel plates of a capacitor connected to a battery. The upper plate is displayed slightly to the left.

State with reason the effect of this movement on the capacitance. (2 Marks)
(b) Figure below an electrical circuit with three capacitors A, B and C of capacitance 4.0µF, 5.0µF and 3.0µF respectively connected to 12V battery.

Determine
(i) the combined capacitance of three capacitors. (3 Marks)
(ii) the charge stored in capacitor A. (2 Marks)
(iii) the potential difference across the capacitor B. (2 Marks)

(a) With the aid of a well labeled diagram, explain how lunar eclipse occurs. (4mk)
(b) Explain why large convex mirrors are placed at certain points in supermarket (2mks)
(c) An object 2.5 m tall is at a point 8m from a pinhole camera. If the distance of the screen is 8.16m from the object,
calculate the size of the image (3mks)
(d) (i) Draw a diagram to show how prisms are used in a periscope (2mks)
(ii) Calculate the critical angle of a ray of light passing from glass to water, if their refractive indices are 2/3 and 4/3 respectively. (3mks)