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Homework Help: Ratio of a ray of light with a refracted ray

  1. Jan 20, 2007 #1
    Hey sum1 please tell me that :

    if d1=Ray of light through a glass slab(dotted line ie extension of unrefracted ray)

    and if d2=Refracted ray

    is d1/d2=mu(refractive index)
  2. jcsd
  3. Jan 20, 2007 #2


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    Staff: Mentor

    How do you divide two light rays? What kind of quantity are [itex]d_1[/itex] and [itex]d_2[/itex]? Angle, distance, wavelength, whatever? :confused:
  4. Jan 20, 2007 #3
    d1 is the length of the unrefracted ray(extension of the incident ray into the glass slab) .d2 is the length of refracted ray
  5. Jan 20, 2007 #4
    Please help!
  6. May 7, 2007 #5
    Friend ! u r saying that what's the ratio of lengths of rays - the extended incident one and the refracted one......in normal diagram u join the initial rays such that triangle formed by normal & inc. ext. =~ triangle by normal & incident(initial) ray.....now....apply geo. u get d1/d2 =sin(90-r) / sin(90-i) which is not equal to mu...as angles formed are i & r & not their complements....
  7. May 7, 2007 #6
    ofcourse i kno that.....but thats wat happens when u do it experimentally
  8. May 7, 2007 #7
    I am sure the angles u took in experiments was pi/4..45....and students often take it....
  9. May 8, 2007 #8
    Well no...this was in two different cases
  10. May 8, 2007 #9
    Length of a ray? How do you define that?
  11. May 8, 2007 #10
    Well.....if u sketch the path of light...and then measure the length it covered
    before exiting the slab
  12. May 8, 2007 #11
    So they are not true.

    Call h be the thickness of the slab, then


    where i and r are initial and refraction angles

    It's clear that d1/d2=cosr/cosi, while n=sini/sinr

    They are equal only if sinrcosr=sinicosi or i+r=90 degrees

    or tani=n

    Just true at Brewster angle!
    Last edited: May 9, 2007
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