REFRACTION

Humans see objects when visible light is reflected off

these objects and enters the eyes.

HOW DO WE SEE?

INTERESTING…

Have you ever noticed that the sun

seems to change colour as it sets?

Or how your legs look different when you

walk in clear water?

This occurs because of the bending of

light!

Light travels in straight lines AS LONG

AS it is traveling in ONE uniform

material.

MEDIUM

The substance or material that light is travelling

through (e.g. water, air, glass, oil)

REFRACTION IS...

angle of

incidence

angle of

refraction

incident

ray

refracted

ray

• the change in direction of light as it moves from

one medium to another…”__________________”

qi angle of incidence

qr angle of reflection

qR angle of refraction

REFRACTION

WHY DOES REFRACTION

OCCUR?

Light travels in a straight line

When light travels from one medium to another,

the speed of light changes.

The result is a change in direction of the light.

e.g. Speed of light in air: 3.00x108 m/s

Speed of light in glass: 2.00x108 m/s

WHY DOES REFRACTION

OCCUR?

• air is less ______ than

glass

• light travels _______ in air

• light travels ________ in

glass

RULES OF REFRACTION

1. The incident ray and the refracted ray are on

___________ sides of the normal and opposite sides of

the boundary between the two media (e.g. where

air/water meet)

RULES OF REFRACTION

2. Light bends _________the normal when it travels from

a less dense to a more dense medium (slows down).

3. Light bends ________ from the normal when it travels

from a more dense to a less dense medium (speeds

up).

Less dense to more dense.

More dense to less dense.

FST

Fast to Slow, Towards normal

Funny Science Teachers

SFA

Slow to Fast, Away from normal

S F Alot

REFRACTION

CONDITIONS NECESSARY FOR

REFRACTION

light must change _________ (change speed when

crossing the boundary)

light must approach the boundary at an ___________

INDEX OF REFRACTION

The _________ of the speed of light in a vacuum (c) to the speed of light in a given material (v).

where…

n is the index of refraction

c is the speed of light in a vacuum (3.00x108m/s)

v is the speed of light in the other medium in metres per second (m/s)

Medium Index of Refraction (n)

air/vacuum 1.00

ice 1.31

pure water 1.33

ethyl alcohol 1.36

quartz 1.46

vegetable oil 1.47

olive oil 1.48

acrylic 1.49

glass 1.52

zircon 1.92

diamond 2.42

gallium phosphide 3.50

Table 1 – Indices of Refraction

EXAMPLES

1. The speed of light in sodium chloride (salt) is

1.96x108m/s. Calculate the index of refraction for

sodium chloride.

2. Calculate the speed of light in olive oil.

3. What is the index of refraction of a substance in which

the speed of light is 8.57 x107 m/s? What substance

could this be?