The likeness of an object carried and formed by light in a mirror is called an image. We all use mirrors at home. You look into the mirror and see your own face inside the mirror. What you see is a reflection of your face in the mirror. We also see reflections of other objects that are in front of the mirror. An image can be seen in the mirror because the light reflected from an object falls on the mirror and it is reflected. So, light incident on any smooth shiny surface like a mirror bounces back into the same medium. This bouncing of light by any smooth surface is called reflection of light. Mirrors change the direction of light incident on them. The image in a plane mirror is the same size and colour as that of the object. Moreover, the distance between the image and the mirror, is the same as the distance between the mirror and the object. Sometimes, we see reflections of trees, buildings and other objects in the water of a pond or a lake.
This activity should be done at night or in a dark room. Ask one of your friends to hold a mirror in his/her hand at one corner of the room. Stand at another corner with a torch in your hand. Cover the glass of torch with your fingers and switch it on. Adjust your fingers with a small gap between them so that you can get a beam of light. Direct the beam of the torch light onto the mirror that your friend is holding. Do you see a patch of light on the other side (Fig. 1)?
Fig. 1. A mirror reflects a beam of light
Now, adjust the direction of the torch so that the patch of light falls on another friend standing in the room. This activity suggests that a mirror changes the direction of light that falls on it. Here is an activity that shows light travelling along straight lines and getting reflected from a mirror.
Fix a comb on one side of a large thermo Col sheet and fix a mirror on the other side as shown in Fig. 2. Spread a dark coloured sheet of paper between the mirror and the comb. Keep this in sunlight or send a beam of light from a torch through the comb. What do you observe? Do you get a pattern similar to that shown in Fig. 2 ? This activity gives us an idea of the manner in which light travels and gets reflected from a mirror.
Fig. 2. Light travelling in a straight line and getting reflected from a mirror
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