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

No rainbow could be observed from the surface of Moon by the astronauts. What could be the possible reason?

What shape are your eye-lenses:

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

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

Among animals, the predators (like lions) have their eyes facing forward at the front of their heads, whereas the animals of prey (like rabbit) usually have eyes at the sides of their head. Why is this so?

Why does the eye-lens not have to do all the work of converging incoming light rays?

Explain why, if we look at objects through the hot air over a fire, the objects appear to be moving (or shaking) slightly.

Write the function of each of the following parts of human eye.

1. Cornea.
2. Iris.
3. Crystalline lens.
4. Ciliary muscles.

When a beam of white light is passed through a prism, it splits to form lights of seven colours. Is it possible to recombine the lights of seven colours to obtain the white light again? Explain your answer.

What is spectrum? What is the name of glass shape used to produce a spectrum?