Practice 15A Answers

1. 18.5°2. a) 27.5° b) glycerine (n = 1.47) c)

12.5°3. 1.47

Physics 15.1Refraction of Light and Snell’s Law

What do you notice about the pencil?

I. RefractionA. Def – The bending of light as it travels from

one medium to another.1. Must be at an angle other than 90°2. If 90° then no refraction3. Occurs when light’s velocity changes

B. Variables1. Θi = angle of incidence

2. Θr = angle of refraction

C. Velocity Changes1. cause light rays to speed up or slow down2. Situations

a. High speed lower speed Result = Light is bent towards the normal

b. Low Speed higher speedResult = Light is bent away from the normal

Concept Question

When trying to catch a fish, should a pelican dive into the water horizontally in front of or behind the image of the fish it sees?*Answer: Behind of the image, because the light entering the water slows down and is bent towards the normal.

Alaskan Natives

E. Barrel Rolling Explanation pg. 563

II. The Law of RefractionA. Index of Refraction – ratio of speed of light in

vacuum to speed of light in a medium.B. Formula n = c / v a. n = index of refraction b. c = speed of light in vacuum c. v = speed of light in mediumC. Table 15-1D. Explains a prism

III. Snells’s Law

A. Def - the relationship between the angle of incidence and angle of refraction of two materials having different index of refraction.

B. Formula n1 sin(Θ1) = n2 sin (Θ2)

C. Variables1. n = indexes of refraction2. Θ = angles of the rays

D. Ex: A light ray traveling through air strikes a piece of carbon disulfide at an angle of 25.0° to the normal. Find the angle of refraction.

15.0°