REFRACTION OF LIGHT

A pencil appears bent or broken when it is partially immersed in water

These are two situation that show the effect produced when light travels from one medium to another

The effects are due to the change of direction of light when light travels from one medium to another.

Refraction of Light• Refraction of light is the bending of a

light rays at the boundary as the rays travel from one medium to another.

• Light rays bend towards the normal when the rays travel from a less dense medium to a denser medium (eg: water to glass)

• Light rays bend away from the normal as it travels from a denser medium to a less

dense medium.

less dense

denser medium

i

r

i = angle of incidence

r = angle of refraction

i > r

Normal lineincident ray

refraction ray

less dense

denser medium

i

r

i = angle of incidence

r = angle of refraction

Normal lineincident ray

refraction ray

• Light rays bend towards the normal when the rays travel from a less dense medium to a denser medium

• Light rays travel much slower in a denser medium

air

kaca

air

water

denser medium

less dense

i

r

i = angle of incidence

r = angle of refraction

i < r

Normal lineincident ray

refraction ray

• Light rays bend away from the normal as it travels from a denser medium to a less dense medium.

• Light rays travel much faster in a less dense medium

denser medium

less dense

i

r

i = angle of incidence

r = angle of refraction

incident ray

refraction ray

air

glass

air

water

When light ray travels from one medium to another, its speed changes. The change in speed of the light ray cause the change of its direction.

ExperimentAim:

To investigate the relationship between the angle of incidence i and the angle of refraction r.

Inference:

The value of sin r is manipulated by the value of sin i

Hypotesis:

The greater the value of sin i the greater

will be the value of sin r.

Aim:

To investigate the relationship between the angle of incidence i and the angle of refraction r.

Inference:

The value of sin r is manipulated by the value of sin i

Hypotesis:

The greater the value of sin i the greater

will be the value of sin r.

Refractive Index

For a light ray travels from vacuum (or air) into a given transparent medium, the ratio of is is always constant.

Snell’s Law,

Refraction index, n = Sin i Sin r

Sini

Sinr

Refractive Index

Laws of Refraction

58.7

40

water

air

30

19.2

air

kaca

60

40.6

water

air

75

40.4

perspex

air

Example

1.

3.

1. 2.

4.

n = speed of lights in the air @ vacuum speed of lights in the medium

Refractive Index and Speed of Light

The speed of light in a vacuum is about 3.0 x 108 ms-1.

Light travels much slower in transparent materials.

Example

• By applying the principle of reversibility of light, light travelling from point A to point B through any system can also travel from B to A along the same path in the reverse direction.

n 1

Sin i 1

Sin r

Sin i Sin r

i r

Answer

ACTIVITY

In groups, do the experiment according to the task given. Explain in detail.

Real Depth and Apparent Depth

water

Apparent Depth,h

Real Depth , H

image

Aplication