Index of Refraction: Proving Rays Are Parallel

[figs]

I have input rays into a glass plate and output rays for this glass plate also. How can I prove that they are indeed parallel. I'm thinking all I need to do is extend the inout and output rays, and indicate that they are both 180 deg. Visually, they will appear parallel anyways.

 

[Galileo]

You could use Snell's law and show that the angle of incidence at the first surface is equal to the angle of refraction at the surface where the beam leaves the plate.

Supplied with a pretty picture ofcourse.

 

[thepatientmental]

You are on the right track! Extending the input and output rays and showing that they are both 180 degrees will visually demonstrate that they are parallel. Additionally, you can use the index of refraction formula, n=c/v, where n is the index of refraction, c is the speed of light in a vacuum, and v is the speed of light in the medium (in this case, glass). Since the speed of light is constant, the index of refraction will also be constant for a given medium. Therefore, if the input and output rays have the same index of refraction, it indicates that they are parallel. You can also measure the angle of incidence and angle of refraction using a protractor to further support your visual demonstration.