Practice 15A Answers 18.5° a) 27.5° b) glycerine (n = 1.47) c) 12.5°

Physics 15.1 Refraction of Light and Snell’s Law What do you notice about the pencil? Physics 15.1 Refraction of Light and Snell’s Law

I. Refraction 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 refraction 3. Occurs when light’s velocity changes Variables 1. Θi = angle of incidence 2. Θr = angle of refraction

C. Velocity Changes 1. cause light rays to speed up or slow down 2 C. Velocity Changes 1. cause light rays to speed up or slow down 2. Situations a. High speed  lower speed Result = Light is bent towards the normal

b. Low Speed  higher speed Result = Light is bent away from the normal

Concept Question Alaskan Natives 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.

E. Barrel Rolling Explanation pg. 563

II. The Law of Refraction Index of Refraction – ratio of speed of light in vacuum to speed of light in a medium. Formula n = c / v a. n = index of refraction b. c = speed of light in vacuum c. v = speed of light in medium Table 15-1 D. Explains a prism

III. Snells’s Law 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. Variables 1. n = indexes of refraction 2. Θ = angles of the rays

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°