Refraction of Light Bending Light When light travels

Refraction of Light

Bending Light • When light travels from one medium into another, it bends. The bending of light in this way is called Refraction.

Gravel (thick medium) Concrete Road (thin medium) Why does light bend? • Assuming that a car travels slower on gravel than on concrete … picture this …

Light is like a marching band

Seeing Refraction

Air Water

Refraction of Light (< of incidence) (< of reflection) Normal Reflected Ray Incident Ray Өi Өr Refracted Ray (< of Refraction) ӨR

A Property of Matter • Some substances cause light to slow down more than others. Hence, these substance cause light to bend more than others.

Index of Refraction • The Index of Refraction for any material is a comparison of the speed of light in the material to the speed of light in a vacuum (c) Speed of light in a vacuum Index of Refraction Speed of light in the material

Examples 1. The speed of light in a vacuum is 3. 0 x 108 m/s. When light travels through ice, it slows down to 2. 29 x 108 m/s. Determine the index of refraction for ice. 2. If the index of refraction for diamond is 2. 42, how fast does light travel as it passes through?

The Law of Refraction • In 1621, Willebrord Snellius derived a mathematical equation to predict how light will refract when it travels between two different mediums.

Snell’s Law Air n = 1. 000293 θR θi Glass n = 1. 52

Snell’s Law Air n = 1. 000293 θR θi Glass n = 1. 52

Snell’s Law Air n = 1. 000293 θR θi Glass n = 1. 52

Snell’s Law Air n = 1. 000293 θR θi Glass n = 1. 52

Example 1. Light enters water (n = 1. 33) from air (n = 1. 000293) at an angle of 25 o. With what angle does it refract? 2. Light travels from glass (n = 1. 52) into another substance at an angle of 45 o. If it refracts at an angle of 26 o, what is the substance?