Where are light-sensitive cells present in abundance and give their function?

Why does the Sun appear reddish early in the morning?

Describe how you could demonstrate that white light is composed of a number of colours.

Nocturnal animals (animals which sleep during the day and come out at night) tend to have wide pupils and lot of rods in their retinas. Suggest reasons for this.

In a certain murder investigation, it was important to discover whether the victim was long-sighted or short-sighted. How could a detective decide by examining his spectacles?

Draw a diagram to show the refraction of light through a glass prism. On this diagram, mark:

1. Incident ray.
2. Emergent ray, and.
3. Angle of deviation.

In the figure given below a narrow beam of white light is shown to pass through a triangular glass prism. After passing through the prism it produces a spectrum XY on a screen.

1. State the colour seen at X and Y.
2. Why do different colours of white light bend through different angles with respect to the incident beam of light?

A narrow beam of light produces a spectrum XY on passing through a triangular glass prism.

1. State the colour at X and Y.
2. Why do the different components of white light bend through different angles with respect to the incident beam of light?

Write the function of the retina in the human eye.

Water in deep sea is blue in colour. Why?