21.

State Archimedes Principle.

A cargo ship is loaded into sea water to maximum capacity. What will happen if this ship is moved to river water? Give a reason for your answer? 

A body of mass 100 g is floating in water. What will be it’s apparent weight? Justify your answer.

The diagram given below shows an object O and its image I. Copy the diagram and draw suitable rays to locate the lens and its focus. Name the type if lens in this case.

i) State Snell’s law.

ii) Calculate the velocity of light in a glass block of refractive index 1.5. ( Velocity of light in air = 3 x 10⁸ m/s.

i) What is an optical fibre?

ii) Give one practical use of an optical fibre. 

Explain briefly how a magnet can be de-magnetised using an alternate current?

State two ways by which the emf in an A.C. generator can be increased. 

i) Give one difference between a chemical change and nuclear change.