How do mirrors show that light travels in a straight line?

Answer 1

if light did not travel in a staight line then the mirror would make the light refract (focus)and since it does not it proves that light travels in a straight line

Answer 2

If this were not the physics forum, I would not give this answer - but it is - so here goes:

This is the type of experiment that gives "proof" to false assumptions or theories. Every test and observation we can perform will show your contention that light travels in a straight line is "true" and we can use mirrors to "prove" it.
This is why Newton's mechanics stood the test of time for so long.

The fact is that on the surface of the earth, light is bent by the earth's gravity toward the earth in an arc that equals a segment of a circle that is one light year in diameter. Obviously, this is not detectable using mirrors and simple observation.

And in space, light takes many twists and turns as it travels through the gravitational fields of different objects.

For all practical applications, if I want a "straight" line for reference in building or foundation layout - I would discount this deviation and use a laser and three mirrors.
It'll be close enough, for sure!

Answer 3

mirrors dont show they reflect