Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Question on light reflection

  1. Dec 22, 2011 #1
    Consider i m moving at a velocity considerable to the speed of light. Above me there is a mirror stretching to infinity . It doesnt move with me. Now if i shine light on the mirror where will the reflected beam hit me?right on me, back of me or infront of me?
  2. jcsd
  3. Dec 22, 2011 #2


    User Avatar
    Gold Member

    You'll need to be more specific in the geometry / distances / speeds for there to be an answer

    EDIT: but if I understand your general drift, it will be "back of you"
  4. Dec 22, 2011 #3


    User Avatar
    Science Advisor

    I assume you move parallel to the mirrors surface and you shine a laser perpendicular to the mirror surface as measured in your rest frame? The laser will hit you then. In the mirrors rest frame it will not be perpendicular to the mirror surface.
  5. Dec 22, 2011 #4


    User Avatar
    Gold Member

    Assume he is a light year from the mirror and is traveling at half of c. Now do you see why I content that geometry/speed/etc are required in order to answer the question?

    EDIT: DOH! Ok, I'm a doofus. I even have a diagram that explains time dilation that also answers this question, and I forgot about it:

    http://www.phinds.com/time%20dilation/ [Broken]
    Last edited by a moderator: May 5, 2017
  6. Dec 22, 2011 #5
    thats correct. As far as distance u can take any distance between me and mirror

    also you can take my velocity any value considerable to speed of light
  7. Dec 22, 2011 #6


    User Avatar
    Gold Member

    see my link in the above post. As AT said, it will hit you
  8. Dec 22, 2011 #7
    haha thats exactly the reason i asked. Although now you have taken back this, for a moment you were convinced of some stationary ether isn't it?i want to know what convinced you about both the stands? because i am perplexed
  9. Dec 22, 2011 #8


    User Avatar
    Gold Member

    No, I have never believed in the "ether" since before I ever had a chance to believe in it I read that it was nonsense.

    I just got the geometry wrong because I forgot to keep the beam of light in your frame of reference.
  10. Dec 22, 2011 #9


    User Avatar
    Science Advisor
    Gold Member

    Why do you think the answer would be any different if there were a stationary ether?
  11. Dec 22, 2011 #10


    Staff: Mentor

    Don't read anything into that. Phinds corrected his statement as soon as he understood the setup clearly.

    There is no evidence for a luminiferous aether.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Question on light reflection
  1. Light Question (Replies: 5)

  2. Light question (Replies: 1)