SNC2D Optics
Name: ________________________
Date: _________________________
Refraction of Light
Refraction:
The speed of light in a vacuum:
c = 3.00 x 108 m/s
Different mediums can change the speed of light, e.g.
 in water, v = 2.26 x 108 m/s
 in acrylic, v = 1.76 x 108 m/s
Rules for Refraction:
1. light bends towards the normal when it SLOWS
DOWN in a medium
2. light bends away from the normal when it
SPEEDS UP in a medium
The Bent Spoon
 Light travels in water slower than in air
(i.e. light travels faster when it leaves the water and into air)
 Therefore, light is refracted _____________ from the normal
 The brain perceives light to travel in a ______________________, and project
light rays backward to a virtual light source behind the real spoon, so we think
that the spoon is ________________ where the spoon really is
Partial Reflection & Refraction
 Some materials (like water, sunglasses, and two-way mirrors) allow light to
undergo partial reflection AND refraction at the same time
 Mirrored sunglasses are coated with a special film that allow you to see out,
but do not allow others to see in
HOMEWORK: 12.1 page 519 #1-7
The Index of Refraction (n):

the ratio of the speed of light in a vacuum (c) to the speed of light in a medium (vmedium)
**n is a dimensionless quantity

also equal to the ratio of the sine of the angle of incidence (i) in a vacuum to the sine of the refracted
ray (R) in a medium
Example #1: The speed of light in sodium chloride is 1.98 x 108 m/s. Calculate the index of refraction for NaCl.
Given:
Required:
Analysis:
Solution:
Paraphrase:
Example #2: Calculate the speed of light in olive oil.
HOMEWORK: 12.4 page 525 #1-10