Physics Projects Color wheel Types of mirrors and uses electromagnetic wave model Reflection telescope model Refraction telescope model Build a 15, 10, and 5 seconds pendulums Research and explain rainbow Due Sunday April 22nd.

CHAPTER 14 REFRACTION Ms. Hanan

Chapter 14 Overview 14-1 Refraction 14-2 Thin lenses Investigate which direction light will bend when it enters another medium and uses Snell’s law to solve problems. 14-2 Thin lenses Solves problems involving image formation by converging and diverging lenses using ray diagrams and the thin-lens equation, explores eye disorders and eyeglasses, and examines the positioning of lenses in microscopes and refracting telescopes. 14-3 Optical phenomena Calculates critical angle; predicts when total internal reflection will occur; explains atmospheric phenomena, including mirages and rainbows; and briefly describes lens aberration.

14-1 Refraction Objectives: Recognize situations in which refraction will occur. Identify which direction light will bend when it passes from one medium to another. Solve problems using Snell’s law.

Vocabulary Refraction Index of Refraction Medium Bending of a Wave Front Angle of Incidence Angle of Refraction.

Review Wave speed equals Reflection is the The focal point is The focal length is Spherical aberration is an effect in which the frequency times wavelength. turning back of an electromagnetic wave at a surface of a substance. the point at which a beam parallel to the principal axes will converge after reflection from a concave mirror. the distance from the focal point to the mirror. image produced by a spherical mirror is blurred. It results from light rays converging at different points when the mirror is not parabolic.

normal air θr θi glass block What is Refraction? The bending of light as it travels from one medium to another

Refraction (bending light) normal air θr θi glass block Refraction (bending light) Light moves at different speeds through different media. When it travels from one medium into another, the change in speed causes the ray to bend. When light traveling through air passes into the glass block it is refracted towards the normal. When light passes back out of the glass into the air, it is refracted away from the normal. The wavelength of the light in the glass is shorter than the wavelength of the incoming light in the air.

The angle of refraction is related to the different speeds: The Law of Refraction The angle of refraction is related to the different speeds: The speed of light in a medium is given by the index of refraction of that medium:

The Refraction of Light Here are some typical indices of refraction:

The Refraction of Light We can now write the angle of refraction in terms of the index of refraction:

The Refraction of Light If light enters a medium of lower index of refraction, it will be bent away from the normal. If the angle of incidence is large enough, the angle of refraction is 90°; at larger incident angles the light will be totally reflected.

The Refraction of Light Basic properties of refraction: http://phet.colorado.edu/en/simulation/bending-light

Sample Problem A light ray of wavelength 589 nm (produced by a sodium lamp) travelling through air strikes a smooth, flat slab of crown glass at an angle of 30.0O to the normal. Find the angle of refraction θr. Given: Unknown:

Use the equation for Snell’s law. Solution Use the equation for Snell’s law.

Homework due next class Assignments Class-work: Practice A, page 493, questions: 1, 2, and 3. Refraction concept review worksheet. Homework: Section review, page 493, questions: 1, 2, 3, and 4. Refraction Problem A additional practice odd questions. Homework due next class