REFRACTION : REFRACTION
Refraction is the bending of light ray as it passes from one medium to another. : Air ?i ?’
glass
?r
Normal Refraction is the bending of light ray as it passes from one medium to another.
Different medium leads to bending light. : As light ray enters a different medium the frequency of light remains the same.
The speed of light changes when passes from one medium to another. Different medium leads to bending light. Index of Refraction (n) = c / v
The ratio of the speed of light in a vacuum to its speed in a given transparent medium. n means how much light slows down in more dense medium.
Slide 4 : Index of Refraction (n) = ?o / ?n = c / v n > 1 because light always travels slower in a substance than in vacuum. Snell’s Law determines the angle of refraction:
ni (sin ?i) = nr (sin?r) nr? ? ?r ? ? the closer the refracted ray to the normal
Slide 5 : Example 1: Find the angle of refraction of a light ray entering diamond (n=2.419) from the following materials at an angle 30o.
Water (n = 1.333)
Cubic zirconia (n = 1.923) Solution: Applying Snell’s Law
ni (sin ?i) = nr (sin?r)
?r=
?r= Given: ni=1.333, ?i=30o , nr=2.419
ni=1.923 16 27
Slide 6 : Example 2: A light ray (589 nm) traveling through air strikes an unknown substance at 60o and forms an angle of 41.42o with the normal . What material is it? Answer:
Ethyl alcohol(n=1.361)
Benzene (n= 1.501)
Ice (n=1.309) v
Homework: Page 567 : Practice 15A/ #1,2&3
Section Review /# 1-4 Homework: Page 567