Index of refraction optics problem

  • Thread starter brad sue
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  • #1
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Hey , I need some indication to solve this problem:

A ray light impinges at a 60 degres angle of incidence on a glass pane of thickness 5mm and index of refraction of 1.54.
the ligth is reflected by a mirror that touches the back of the pane. By how much is the beam displaced compared with the return path it would have if the pane were absent?


I found the angle x --normal with the refracted ray. x= 34.2 degres.
I also found the length of the ray entering in the glass (up to the mirror)--L= 5.10-3\ cos(x)=6.0 10-3m

From here what can I do to find the displacement?
I attach a picture of the problem.

Thank you
 

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  • #2
Edit: Ah I misread the question (didn't realise there was a mirror).
 
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  • #3
See my image, where the capital letters are points and 'd' is the displacement.

http://img89.imageshack.us/img89/8789/optics9xq.gif [Broken]

In the situation [tex]\angle EBF = 90 - 60 = 30[/tex]. Which indicates that [tex]\angle BEF = 180 - 30 - ( 90 + 30 ) = 30[/tex] as points BEF form a triangle (which have a maximum of 180 degress, so from that subtract [tex]\angle EBF[/tex] then [tex]\angle BFE[/tex]).

Now I'm pretty sure [tex]\angle FCE[/tex] forms a right angle. If they do you then get a whole series of right angle triangles and using trignomentry and pythagoras's theroem enable you to work out "d".

This is probably a cumbersome way of going about it, but its the only way I can see at the moment.
 
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  • #4
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Beam me down said:
See my image, where the capital letters are points and 'd' is the displacement.

http://img89.imageshack.us/img89/8789/optics9xq.gif [Broken]

In the situation [tex]\angle EBF = 90 - 60 = 30[/tex]. Which indicates that [tex]\angle BEF = 180 - 30 - ( 90 + 30 ) = 30[/tex] as points BEF form a triangle (which have a maximum of 180 degress, so from that subtract [tex]\angle EBF[/tex] then [tex]\angle BFE[/tex]).

Now I'm pretty sure [tex]\angle FCE[/tex] forms a right angle. If they do you then get a whole series of right angle triangles and using trignomentry and pythagoras's theroem enable you to work out "d".

This is probably a cumbersome way of going about it, but its the only way I can see at the moment.
Make more sense now. Thank you I will try to go from here.
B.
 
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