A student sitting in the last row of the class-room is not able to read clearly the writing on the
blackboard.

1. Name the type of defect he is suffering from.
2. How can this defect by corrected?

The power of a lens is +1.5D. Name the type of defects vision that can be corrected by using this lens. Find the focal length of the lens.

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

The picture given here shows a person wearing 'half-moon' spectacles. What sort of eye-defect do do you think he has? Why are these particular spectacles useful to him?

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?

Why do we see a rainbow in the sky only after rainfall?

Explain why the planets do not twinkle but the stars twinkle.

Draw a ray diagram to show the refraction of light through a glass prism. Mark on it,

1. The incident ray,
2. The emergent ray,
3. The angle of deviation.

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?