Refraction lecture

OBJECTIVES: Explore the refraction property

of light. Determine what causes

bending of light. Relate refraction of light to real

life experiences.

REFRACTIONIs the BENDING of light as it passes OBLIQUELY from one medium to another of different optical density.

Examples:Air to waterWater to airWater to glass

Why does LIGHT bend?

Light bends because….1. Of the change in

MEDIUM.Light bends as it moves from one medium to another like from air to water.

Light bends because….1. It changes

speed as it encounters a different medium.

Light does not bend when it enters the medium perpendicularly, however it slows down.

glassairIncident

ray

Refracted ray

Normal line

1

2

Angle of incidence

Angle of refraction

What determines the bending of light?

When light enters a medium of greater optical density, it bends towards the normal.

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 mediumLight rays travel much slower in a denser medium

air

glass

air

water

When light enters a medium of lesser optical density, it bends away from the normal.

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

LIGHT ENTERING WATER FROM AIR

INDEX OF REFRACTION (n).The ratio of the speed of light in vacuum to the speed of light in the material.

Speed of light in vacuumSpeed of light in material

= =n Cv