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: Question on ray optics

  1. Sep 19, 2005 #1

    smn

    User Avatar

    Hello there,

    I've been working on the following question:

    A thin prism with a refraction index of n=1.41 has a top angle of 5.7 degrees. Find the angle of deflection for a light ray that falls on the prism surface : (a) normally
    (b) At an angle of 4 degrees

    I have worked out the second part (b) using snell's law and some geometry techniques and get the answer of 2.3 degrees which i know is correct.

    The first part of the question (a) i am struggling to workout although i do know the answer is suppose to be again, 2.3 degrees.

    If anyone can shed any light (excuse the pun!) on the first part (a) of the question it would be greatly helpful.

    Regards

    Smn
     
    smn, Sep 19, 2005
  2. jcsd
    Phys.org - latest science and technology news stories on Phys.org
  3. Sep 19, 2005 #2

    George Jones

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    If the light ray falls normally on the surface (i.e., at right anglest to) there is no refraction - the light ray (ignoring partial reflection) just goes straight through. Consequently, only refraction at the second surface has to be considered. Use: geometry to relate the apex (top) angle to the angle of incidence at the second surface; Snell's law.

    Regards,
    George
     
    George Jones, Sep 19, 2005
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook