Question

Describe an experiment to show that light travels in a straight line path.​

Answer 1

Take three square cardboards A, B and C each side of about 5 cm. Take a pin and make a small hole in each cardboard at the same height. Suspend the cardboard piece such that each hole is at the same height, as shown in fig A. ​
​Pass a string through the holes and pull it. This makes the three holes in a straight line. Now take the string out. Place the lighted candle near one of the cardboard. Look at the candle flame from the other side of the cardboard C.​
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The candle flame is clearly seen. Now slightly displace one of the cardboard says B so that the holes no longer remain in a straight line. ​
Again look at the candle from other side of the cardboard C. Now you do not see candle flame. The reason is light travels in a straight line but holes in cardboard A, B and C are not in a straight line.​