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

Homework Help: Angle between the incident ray and the reflected ray?

  1. Feb 22, 2005 #1
    A ray of light strikes a mirror at an angle of 53 degrees to the normal.

    A) what is the angle of reflection?
    Ans: 53 degrees

    B) what is the angle between the incident ray and the reflected ray?
    Ans: 53+53 = 106 degrees

    C) A ray of light has an angle of incidence of 30 degres on a block of quartz and an angle of refraction of 20 degrees. What is the index of refraction for this block of quartz?
    Ans: Nr = (1.54) (sin 30) / (sin20) = 2.25

    are the above answers correct?

    Last edited: Feb 22, 2005
  2. jcsd
  3. Feb 22, 2005 #2
    Where did the 1.54 com from in:?
    "Nr = (1.54) (sin 30) / (sin20) = 2.25"
    Is the light ray in air before it hits the quartz? I am assuming so. So one of your indexes of refraction in the above equation should be 1 since 1 is the index of refraction of air.
  4. Feb 22, 2005 #3
    but.... dont i have to specify the index of refraction of quartz which is 1.54..... i dont see where the index of refraction of air would fit in..

    EDIT: nevermind figured it out... so basically it'll be Nr= sin 30/sin20?
    Last edited: Feb 22, 2005
  5. Feb 22, 2005 #4
    Yes that looks good with the edit
  6. Feb 22, 2005 #5
    great.. thanks much :)
  7. Feb 23, 2005 #6
    No problem and thank you for the response at the end it is nice to know that I helped.
  8. Feb 23, 2005 #7


    User Avatar
    Science Advisor

    The problem ASKED for the index of refraction of quartz! Actually there are different kinds of quartz that have slightly varying indices of refraction. Since sin(30)/sin(20)= 1.46, that's not too far off your value.
  9. Feb 23, 2005 #8
    Yeah I looked it up. It think this type of quartz is Fused quartz, do either of you know the difference between fused quartz and just plain old quartz?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook