A person can read a book clearly only if he holds it at an arm's length from him. Name the defect of vision:

1. If the person is an old man.
2. If the person is a young man.

Why are the ‘danger signal’ lights red in colour?

A man can read the number of a distant bus clearly but he finds difficulty in reading a book.A man can read the number of a distant bus clearly but he finds difficulty in reading a book.

1. From which defect of the eye is he suffering?
2. What type of spectacle lens should he use to correct the defect?

What is atmospheric refraction?What causes atmospheric refraction?

Draw ray diagrams each showing:Hypermetropic eye.

Why does the sun appear reddish early in the morning? Will this phenomenon be observed by an observer on the moon? Justify your answer with a reason.
OR
Why does sun appear reddish at sunrise? Give reason.

What are the advantages of having two eyes instead of just one?

Explain why, the sun can be seen about two minutes before actual sunrise. Draw a diagram to illustrate your answer?

Explain why, we cannot see our seats first when we enter a darkened cinema hall from bright light but gradually they become visible.

State the role of ciliary muscles in accommodation.