If a light of a single colour is passed through a liquid having a piece of glass suspended in it, so on changing the temperature of the liquid, at a particular temperature, the glass piece is not seen.

(a) At what situation, the glass piece will not be seen?

(b) Why the light of a single colour is used?

(c) How can you define the term refractive index of a medium? State whether it can be less than 1 or not.

A ray is directed towards a lens as shown in the figure below. The lens is being depicted as a combination of a glass slab and two prisms.

Answer the following questions.

(a) Name the lens which is formed by this combination.

(b) What is PQ line called?

(c) Complete the ray diagram.

(d) The incident ray after refraction actually meet or appears to meet line PQ at a point. What is this point called?

(a) Mention one difference between reflection of light from a plane mirror and total internal reflection of light from a prism.

(b) When an empty test tube is placed in a beaker of water and viewed from above, its surface appears as a mirror. Explain.

The diagram given below shows a lens as combination of glass prisms of different refractive indices. Copy the diagram and answer the following questions.

(a) Name the lens formed by the combination.

(b) Complete the ray diagram when AB is between optical centre and 2F.