Refraction of Light

Chapter 15.1

Reflection is the turning back of light.

All objects reflect some or all of its light.

Refraction is the bending of light. Transparent objects bend light when passing

through them (refraction).

Reflection vs. Refraction

Refraction – The bending of wave disturbance

as it passes at an angle from one medium into another.

Ex: Light passing from air to water bends as it goes

from one medium to another.

Refraction

Imagine two wheels on an axel rolling across

two different surfaces.

Refraction Example

Blacktop

Grass

Blacktop

1

2

3

1. Left Wheel hits the grass first and slows down

as the right wheel continues at its original speed. This causes the wheels and axel to change from its original direction.

2. Once both wheels are in the grass, they both travel at the same speed (No Bending).

3. Left wheel leaves the grass first making it speed up again as the right wheel is still slowed by the grass causing the wheels and axel to turn again. Back to its original direction, just shifted.

Explanation

The same thing happens to light when it

passes from one medium to another just as the wheels traveled from one surface to another.

Ex: Air to Glass Air to Water Water to Air Etc…

Refraction Explanation

The index of refraction is a ratio of how much light changes it’s speed which is directly related to how much light will bend.

The Law of Refraction

There is no bending of light when the index of refraction is equal to one (n = 1).

Index of refraction is unitless. For all index of refraction values greater then

one (n > 1), light bends from it’s original path.

As the value of “n” increases the bending of light increases.

Ex: Diamond: n = 2.419 Water: n = 1.333 Air: n = 1.000293

Index of Refraction

The wavelength of light also effect the index

of refraction. Ex:

White light passing througha raindrop let (water) and creating a rainbow.

ROYGBIV Red – Low Bend Violet – High Bend

Wavelength and Refraction

Angles are always measured from the normal to the ray of light.

Snell’s Law

Snell’s Law Diagram

𝜃𝑖

𝜃𝑟

First Medium:

Second Medium:

Normal Line

AIR

Water

A light ray traveling through air strikes a

smooth, flay slab of crown glass at an angle of 30 degrees to the normal. Find the angle of Refraction.

Snell’s Law Example

Example Answer