27 Nov 2019

You will be utiizing a basicoptic system.

The index of refraction of theplastic cylindrical lens depends on wavelength. Choose an anglewhich gives a good color separation and measure the index ofrefraction for blue and red light.

Question:How big is the difference in indices of refraction? How good is theapproximation that n is constant for thismaterial?

If this question doesnt make sense..then just answer ittheoretically speaking. That is how would we go about checkingwhether or not it conforms with the n as the constant for thematerial... Thanks!

Background info:


The Law ofReflection

The law of reflection states that for a plane mirror, the angle ofincidence is equal to the angle of reflection, and that the tworays lie in a plane.



. A light ray perpendicular to the surface has an angle ofincidence 0°.

The Law of Refraction –Snell’s Law

A ray of light passing from one substance (index ofrefraction

n1)into another (index of refraction n

2) across a plane boundary will be refracted. The angle the raymakes in one medium will be related to the angle in the secondmedium by the equation below, and that all rays lie in aplane.


Total InternalReflection

A ray incident on a medium with lower index of refraction willbe

totally internally reflected if sin θ1> n2/n1.There will be no transmitted beam for this incident angle. Ameasurement of the critical angle for total internalreflection can be used to determine the index of refraction of the substance.If n

2 = 1 (air), then the critical angle is:

sin θc = 1/


1. (3)

Polarization byReflection – Brewster’s Angle

If the angle between the reflected and refracted rays is 90°,then

tan θ

B = n2/n

1. (4)

At this angle, only light with polarization out of the plane ofreflection and refraction will be reflected. The reflected lightwill be completely polarized.


Refractionof Light Rays


Incidentand Reflected Rays


Always measure the angles with respect to the surface

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