1. REFRACTION PART 1 Refraction Part 1 Read sections 12.1 and 12.4 in text. Definition: the bending or change in direction of light when it travels from one medium into another of different density. The more optically dense the substance is the greater the bending of light.

2. REFRACTION

3. NOTE: Draw the NORMAL PERPENDICULAR to the surface. All angles are measured from the normal to the incident ray or the refracted ray. Angle of Refraction: the angle between the Refracted ray and the Normal

5. What Causes Refraction ?

6. Rules for Refraction: The incident ray, the refracted ray and the normal all lie in the same plane. The incident ray and the refracted ray are on opposite sides of the line that separates the two media. Light bends TOWARD the normal when the speed of light in the second medium is LESS than the speed of light in the first medium. Light bends AWAY from the normal when the speed of light in the second medium is greater.

7. SPEED OF LIGHT Speed of Light Light can go into a more optically dense substance or come from it. When light bends it also undergoes a speed change. In the 1800s, James Clerk Maxwell postulated that the speed of light was 3.0 x 10 8 m/s in a vacuum. In 1905 Albert Einstein postulated that nothing can travel faster that the speed of light in a vacuum. This means that in all other substances the speed of light is less. The refraction of light is a result of the slowing down of light in a more optically dense substance.

8. Index of Refraction for a medium Defined as the ratio of the speed of light in a vacuum to the speed of light in that medium. Mathematically it is represented as n= C V

9. The measure of the slowing of the speed of light is called the “index of refraction” and is represented by the letter ‘n.’ n = c v n – index of refraction (no units) c – speed of light (3.0 x 10 8 m/s) v – speed of light in the medium

10. Index of Refraction Table

12. Extra Sample Problem What is the speed of light in water given that water has an index of refraction of 1.33? G:n = 1.33 c = 3.00 x 10 8 m/s R:v = ? A:v = c/n S:v = 3.00 x 10 8 m/s 1.33 v = 2.26 x 10 8 m/s P:Therefore the speed of light in water is 2.26 x 10 8 m/s.

13. Classwork/Homework Six practice problems on page 6 of this Wiki. Page 519 #’s: 2,3,4,7 Page 525 #’s: 2-7