(a) Explain how neon signs can be produced.

(b) State two factors on which the colour of light from a fluorescent tube depend.

Explain why a direct electric current is used instead of an alternating current in electroplating.

(a) (i) What is meant by a machine?

(ii) List two examples of a simple machine.

(iii) Explain the statement — the velocity ratio of a machine is 5.

(b) (i) Define the efficiency of a machine.

(ii) Explain why a machine can never be 100% efficient.

(c) A screw jack, 25% efficient and having a screw of pitch 0.4 cm is used to raise a load through a certain height. If in the process, the handle turns through a circle of radius 40.0 cm, calculate the;

(i) velocity ratio of the machine; (ii) mechanical advantage of the machine; (iii) effort required to raise a load of 1000 N with the machine. [Take \(\pi\) =3.14]

 (a) (i) Define relative density.

(ii) List three characteristics of pressure in a liquid.

(b) The horizontal door of a submarine at a depth of 500m has an area of 0.4m\(^{2}\). Calculate the force exerted by the sea water on the door at this depth. [Relative density of sea water = 1.03 ] [Atmospheric pressure =- 1.01 x 10\(^{5}\) Nm\(^{-2}\)] [Density of pure water = 1000kgm\(^{-3}\)] [g = 10ms\(^{-2}\)]

(c) (i) List three effects of heat other than expansion.

(ii) Explain saturated vapour pressure.

(iii) A heating coil of resistance 20 \(\Omega\) connected to a 220 V source is used to boil a certain quantity of water in a container of heat capacity 100 J kg\(^{-1}\) for 2 minutes. If the initial temperature of the water is 40° C, calculate the mass of the water in the container. [specific heat capacity of water = 4.2 x 10\(^3\) Jkg\(^{-1}\) K\(^{-1}\)] [assume boiling point of water = 100°C]

(a) State Heisenberg's uncertainty principle

(b) mention two phenomena that can only be explained in terms of the particulate nature of light