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

Experiment :

Place a lighted candle on a table. Take a drinking straw. Close one eye and look at the candle flame through the straw from the other eye. The flame is clearly visible.

Now, bend the straw in the middle and again look at the candle flame through the straw. The flame is not visible now. The reason is that light travels in a straight line path. When the straw is bent, the light of the candle flame does not reach our eye.

Conclusion : Light travels in a straight line path.