Suppose you are in a dark room. Can you see objects in the room? Can you see objects outside the room? Explain.

State whether the following statements are true or false:

(a) The moon is an illuminated object.

(b) Diffuse reflection means the failure of the laws of reflection of light.

(c) In a kaleidoscope, a pattern seen once can never be seen again.

Fill in the following blanks with suitable words:

(a) The angle of ................ equals the angle of reflection.

(b) A person 1 m in front of a plane mirror seems to be......... m away from his image.

(c) If you touch your.........ear with right hand in front of a plane mirror, it will be seen in the mirror that your right ear is touched with..........

(d) The size of pupil becomes...........when you see in dim light.

(e) Night birds have.........cones than rods in their eyes.

(f) The image of an object persists on the retina of an eye for about.........second even after the object has disappeared.

(g) If the still pictures of a moving object are flashed on our eyes at a rate faster than..............pictures per second, the eye perceives the object as moving.

(h) In a movie, the still pictures in proper sequence are projected on the screen usually at the rate of ...........pictures per second.

What makes things visible to us? Why cannot we see a book which is placed (a) behind a wooden screen, and (b) in a dark room?

We can see the sun because it is glowing. How are we able to see the moon?