5
$\begingroup$

So, when I point a laser at a piece of wire (pointed at a specific angle), a circle of light appears on a wall behind it (see image below). I am trying to see why this happens and if there are any readings on this. Could anyone give some tips on what I should search for or any references?

enter image description here
(screenshot from this youtube video)

So this is a problem for a physics tournament, but I haven't tried it myself yet. However I have found a video depicting what I mean.

$\endgroup$
  • 1
    $\begingroup$ A reference for what, exactly? It's not all clear to me what it is you are doing that you want to search. $\endgroup$ – Kyle Kanos Jan 28 '15 at 1:27
  • $\begingroup$ Sorry for being so unclear, I'm new to this and was in a rush typing up the question. Will edit shortly. Thanks! $\endgroup$ – Tao Tien Jan 28 '15 at 13:49
  • $\begingroup$ This is a problem for a physics tournament, and the problem is basically written exactly as I asked, so I'm completely lost too. $\endgroup$ – Tao Tien Jan 28 '15 at 14:08
  • 2
    $\begingroup$ I see what you mean now, the video really helped. I've added a screenshot from the video so that others can see what you mean without clicking away (as well as add some grammar fixes). $\endgroup$ – Kyle Kanos Jan 28 '15 at 14:20
  • 1
    $\begingroup$ I suspect that it's going to be related to diffraction about the sharp point of the pin. $\endgroup$ – Gremlin Jan 29 '15 at 11:03
5
$\begingroup$

So I did it myself and figured it out. It's just really simple reflection.

enter image description here

Basically the wire acts as a mirror, albeit a curved one. Because the light from a laser is straight, we won't have messy light. When a laser reflects off of a flat surface, it keeps going straight. However when it reflects off a small curved surface (i.e a wire), the laser rays all go different ways, and create a circle of light.

$\endgroup$
  • $\begingroup$ From the screenshot, the circle looks closed and uniform in intensity, which is odd if reflection is the sole cause. $\endgroup$ – user27118 May 21 '15 at 17:46
  • $\begingroup$ But how about the dark fringes? $\endgroup$ – David 2000 Jul 1 '15 at 23:46

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.