If i would point a basic red laser at a wall i would see a red point, but how? The photons from the laser cant reach my eye unless the laser is aimed very specificlly, Other photons can't bounce of the laser into my eye since light doesnt bounce of from light, so what is happening?

  • $\begingroup$ Why don’t you think the laser light scatters off the wall? $\endgroup$
    – Jon Custer
    Nov 11 '20 at 22:45
  • $\begingroup$ Photons sometimes act like pingpong balls and bounce off the wall straight into your eye! $\endgroup$
    – my2cts
    Nov 11 '20 at 22:49
  • $\begingroup$ It does but in the direction of the same angle it hited the wall so it probablly wont be in the direction of my eye $\endgroup$ Nov 11 '20 at 22:49
  • 1
    $\begingroup$ You may be interested in the wiki article on diffuse reflection. $\endgroup$
    – J. Murray
    Nov 11 '20 at 23:18
  • $\begingroup$ Think about why you can see the wall if light from the sun bounces off it, but the sun isn't at exactly the angle such that the wall would (if it were a mirror) reflect its light into your eyes. $\endgroup$
    – The Photon
    Nov 11 '20 at 23:36

You missed an important difference between a mirror and a wall.

reflection from mirror
A mirror is a very smooth surface. Therefore, when a laser beam hits the mirror, then its rays are all reflected to the same direction. You can see the reflected laser light only when your eye is at the right place. (Do not actually try this. It would damage your eye.)

enter image description here
A wall is a very rough surface. Therefore, when a laser beam hits the wall, then its rays are all reflected to different directions. You can see the reflected laser light from everywhere.

  • 4
    $\begingroup$ It's worth mentioning that, as you say, you can't see the spot where a laser impacts a mirror unless your eye happens to be in exactly the right place - but this is not an experiment that you should actually perform, because you could permanently damage your vision. $\endgroup$
    – tparker
    Nov 12 '20 at 1:31
  • $\begingroup$ @tparker yes, of course. $\endgroup$ Nov 12 '20 at 6:37
  • $\begingroup$ Really nice answer. $\endgroup$ Nov 14 '20 at 6:24

There are three different ways in which you can actually " see" a laser

  1. The laser beam directly and receiver Rai without any obstruction (extremely dangerous and therefore should never be tried)

  2. A laser beam bounces off that is gets reflected from a smooth or rough surface and a small fraction of it reaches your eyes.

  3. A laser beam is scattered as a result of the presence of particles in the medium. You throw plenty of dust in the path of a laser beam and then see some of the laser light getting scattered so that you are able to see the beam.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.