Reflection vs. Refraction

RefractionRefraction of Light: Bend or

change direction1. As light rays enter a new

medium the cause light to bend

2. The denser the medium – the slower the light travels

3. Index of Refraction: a measure of how much a medium bends the light that travels through it.

4. The faster the beam, it will bend away from normal, the slower the beam, it will bend toward the normal.

A mirage is a visual distortion produced by the refraction of light.

Some mirages produce a mirror or a watery image, and others may make an object appear larger or smaller, nearer or further away.

The ray model says…

Light has four different ways in which it can interact with matter.

Medium 1 Medium 2

Reflection

Light has four different ways in which it can interact with matter.

Medium 1 Medium 2

Refraction

Light has four different ways in which it can interact with matter.

Medium 1 Medium 2

Scattering

Light has four different ways in which it can interact with matter.

Medium 1 Medium 2

Absorption

Reflective Objects

Reflection

Reflection off Paper Reflection off a Mirror

Regular ReflectionDiffuse Reflection

Law of Reflection

i

rNormal - an imaginary line drawn perpendicular to the surface

Reflections in a Mirror

Q

An observer observes a light source S in a mirror. Where does he perceive the mirror image of S to be located?

S

●1

●2

●3

●4

How big does a mirror have to be in order to see your entire length in it?

Half His Height!

To see more of her head in the mirror, she …

1. should hold the mirror closer

2. should hold the mirror farther away

3. needs a bigger mirror

Refraction

i

R

Refraction

As light travels from one medium to another, the speed of light changes and the light bends accordingly.

n1 sin I = n2 sinR

Snell’s Law: The Law of Refraction

Index of Refraction of the media in which the angle of incidence is

Index of Refraction of the media in which the angle of refraction is

Index of Refraction

mediainlightofspeed

spaceinlightofspeedrefractionofindex

Cannot be less than 1.00

Air = 1.00 Glass = 1.5

Water = 1.33

Q

Bruno wishes to “spear” a fish with a laser. Should he aim the laser beam…

1. above 2. below 3. directly at

the observed fish to make a direct hit?

Light is incident on a block of glass as shown. Which ray is the refracted ray?

1.2.

3.

4.

Calculate the critical angle θ from glass (n=1.5) to air.

θ

1. 52.9o 2. 41.8o 3. 32.2o

4. 22.5o 5. 12.3o

Calculate the critical angle θ from glass (n=1.5) to air.

θ

1. 52.9o 2. 41.8o 3. 32.2o

4. 22.5o 5. 12.3o

n1 sin I = n2 sinR

1.5 sin I = 1.0 sin 90

sin I = .667

I = 41.8

Fiber Optics

Fiber optics uses total internal reflection