# Homework Help: My old question on Optic

1. Feb 8, 2009

### HoangFat

Well, this is the question from the end term exam of the Optic 1 year 1 ago that I got from the senior, we (me and my friends) get confused. I try to slove this problem by Geometry Optic but the final equation cant slove (if sloved it will be loooooong to slove on the short time). I think abount using Fremat's Principle, but I can't detect the way to mash it.

so :
The CALCITE block with the Optic Axis parallel with the surface,the thickness is H
(ordinary index N and extraordi index Ne
A beam of light trikes the surface at an angel of incidence of Alpha from the vertical., the plane which keep the beam perpendicular with the OA.
2 Out beams,the ordinary beam and the extraordinary beam, parallel with the distant L !

>>Find Alpha

Fig: http://img178.imageshack.us/my.php?image=opticko7.jpg"

Yep, that all !

Hmmm.. This is my 1st post, I hope I didnt post a homework (yeah this is not homework).
And my English is bad T.T

Last edited by a moderator: Apr 24, 2017
2. Feb 9, 2009

### Redbelly98

Staff Emeritus
Welcome to PF

Are you familiar with Snell's Law? I think that will be useful here.

3. Feb 9, 2009

### HoangFat

Ya ! I used the Snell's law in Geometry Methol, but I think using the wave mothol in sloving,
If you use the Sneel's law you 'll got the unsloveable quation T.T