CBSE Class 6 Answered

Fix a lighted candle on a table. Take a rubber tube, stretch it straight and look through it at the flame of the candle with one eye (keeping the other eye closed) [see Figure (a)]. We will find that when the rubber tube is straight, we can see the light of candle flame through it.

Now, bend the rubber tube a little and look through it at the candle flame again [see Figure (b)]. We cannot see the light of candle flame through a bent rubber tube. This means that the light of candle flame can travel through the hole of straight rubber tube but not through the bent rubber tube. From this observation we conclude that light travels in a straight line.