• Question: How does a laser work to 'push' things

    Asked by markbarwell to Andrew, Daniel, Hayley, Natalia, Peta on 15 Nov 2011.
    • Photo: Daniel Scully

      Daniel Scully answered on 15 Nov 2011:

      Lasers fire light, which is made up of particle called “photons”.
      When photons bash into things they give them a little push just like anything else, it’s just a very small push so you don’t notice normally.

      But if you set up an object in the right way with a powerful laser you can still make something measurably move

    • Photo: Peta Foster

      Peta Foster answered on 15 Nov 2011:

      Daniel is right… photons have momentum which you have probably covered in class… this momentum can be passed to an object in the same way as you can push things along the desk with your hand.

      My laser is very intense and has such large amount of concentrated photons at the focus that it instantaneously rips apart the atoms and punches out the electrons from the target! This is done within a 1/1000 000 000 000 000 of a second!

      People have talked about using the light pressure to power ships in space… where you would have an enormous sail that the light could push on 🙂

      One experiment we have just done is using the laser to punch these electrons out so fast that they fly away at speeds close to the speed of light… now when you look into a mirror it is actually the electrons that the light is interacting with and what we found is that we can actually use the fast moving electrons as a mirror!

      Now i think it was Einstein that first talked about a mirror travelling at the near the speed of light. He wondered what would happen if you looked at yourself in it… do to thi you would be looking at light from your face reflecting off the mirror! So what we have done if made this flying mirror and we have bounced light off it… It was very exciting to get to see something i think Einstein would have loved to be we find that we can compress the light coming off so if we illuminated you with red light… we would get blue light (or much shorter) coming out 🙂

      I hope that explained a bit about lasers pushing things 😀

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