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

What is the correct way to draw this internal reflection

  1. Mar 1, 2015 #1
    image.jpg
    image upload no size limit

    http://postimage.org/] image.jpg [/PLAIN] [Broken]
    image hosting adult


    The answer is saying the following,

    initial reflection + 0 or 1 further reflection only, not at lower surface

    must be straight and reach within 1cm of end.
    ---------
    How come 0 or 1 reflection only ? The length is long to take only one reflection!

    I also attached a photo of how I think it should be drawn.

    Thank you for your help!
     
    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Mar 1, 2015 #2

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    Looking at your drawing, it seems to me that the first reflection is not symmetrical.. Did you draw a Normal and get the angles i and r the same.? Your picture seems to bring the first reflection to hit the lower surface much too soon. I could believe the 'real answer' more than yours. (That third reflection of yours looks even worse.)
     
  4. Mar 1, 2015 #3
    Actually this is not my drawing . I found it in the internet but this is exactly the way I have drawn too.
     
  5. Mar 1, 2015 #4

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    Well, it can't be right if it doesn't follow the laws of reflection, can it?
     
  6. Mar 1, 2015 #5
    I agree. It doesn't follow the law of reflection !
     
  7. Mar 1, 2015 #6

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    So it's wrong. Draw it so it does follow the law and you should get the right answer. :wink:
     
  8. Mar 1, 2015 #7
    What do you think about the asnwer in the mark scheme?
     
  9. Mar 1, 2015 #8

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    I can't be bothered to draw it out but it looks OK when I do it 'by eye'. Have you drawn it out carefully and do you disagree with it?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: What is the correct way to draw this internal reflection
Loading...