1. Warm Up 1) ROY G BIV represents what?
2) Why is ROY G BIV in that order? (why not VIRG BOY?)
3) Why does nature put ROY G BIV in that order?

2. Goals Discuss how the color of light is related to its frequency
Define Index of refraction, and the speed of light in a material
Work on Snell’s Law and Refraction

3. Index of refraction
A number that describes the speed of light in a material
‘n’ = index of refraction
nair = 1
nwater = 1.33
Nglass often around 1.5

4. Speed of Light in a Material
v = c / n
Example: What is the speed of light in water?

5. Practice
What is the speed of light in a material whose index of refraction is 1.7?
What is the speed of light in a material whose index of refraction is 1.2?

6. Color and Frequency The color of light is determined by its frequency
When light goes into another material, its wavelength and speed change, but its frequency remains constant
Red – Orange – Yellow – Green – Blue – Indigo – Violet
Low frequency  High frequency

7. Snell’s Law
Describes how much light bends (refracts) when it changes mediums
n1 sin θ1 = n2 sin θ2
Example: What is the index of refraction of the second material when light goes from air (n = 1) into a second material at a 25 degree angle, and gets refracted through a 15 degree angle?

8. Practice
What is the index of refraction of the second material when light goes from air (n = 1) into the material at a 20 degree angle and gets refracted through a 15 degree angle?
Example: What is the index of refraction of a mystery liquid when light goes from water (n = 1.33) at a 30 degree angle and gets refracted through a 40 degree angle?

9. Cool Down 1) What is Refraction?
2) Out of all of the colors which color of light carries the most energy?
3) How do you calculate the speed of light in a material?