Question

Show an experiment which proves light always travels in a straight line.

Answer 1

Showing an experimental view that proves light always travels in a straight line.

The demonstration of the pin-hole camera. See image.

A pinhole camera is a simple camera without a lens but with a tiny aperture, a pinhole-effectively a tight proof box with a small hole in one side light from a scene passes through the aperture and projects an inverted image on the opposite side of the box, which is known as the camera obscure effect.

Perform an experiment taking tree wooden planks(small-sized) made a small ole in all the three planks in the center. I arranged all the three one after the other in straight, having a space of some distance between each plank, then I lit a candle and placed it before the first plank and asked one of my friends to see through the hole from the third plank. He can clearly see the candle flame, then what I did is move one of the planks (second) and he could not see the flame. It proves that the light travels in a straight line, the same phenomena take place in the Pinhole camera.