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?

What shape are your eye-lenses:

1. When you look at your hand?
2. When you look at a distant tree?

Your friend can read a book perfectly well but cannot read the writing on blackboard unless she sits on the front row in class.

1. Is she short-sighted or long-sighted?
2. What type of lenses-converging or diverging-would an optician prescribe for her?

What happens when a beam of sunlight enters a dusty room through a window? Explain your answer.

Why does the Sun appear reddish early in the morning?

Five persons A, B, C, D and E have diabetes, leukaemia, asthma, meningitis and hepatitis, respectively.

1. Which of these persons can donate eyes?
2. Which of these persons cannot donate eyes?

Draw ray diagrams each showing:Hypermetropic eye.

Explain why, when it is getting dark at night, it is impossible to make out the colour of cars on the road.

A star sometimes appears brighter and some other times fainter. What is this effect called? State the reason for this effect.