Refraction

Refraction Although light travels in straight lines, it bends when it passes from one medium to another Medium (plural “media”) - the material that is being used or undergoing a process

Refraction Refraction = the bending of light rays as they pass between two different media

Refraction Refraction occurs due to changes in the speed of light in different mediums Different media slow down light by different amounts The more that light slows down, the more the light is refracted

Refraction in Water Light rays change direction at the surface of the water The image of the chest appears to be more shallow than the actual chest….illusion of apparent depth

Speed of Light In a vacuum: However, it is impossible for light to move at this speed when particles get in the way… or

Refraction The particles in a medium slow down the passage of light waves Light only refracts at the boundary when it is entering or leaving a medium

(since units cancel, a refractive index does not have any units) Index of Refraction Index of Refraction = the amount by which a transparent medium decreases the speed of light or (since units cancel, a refractive index does not have any units)

Given: Speed of light in glass = 1 Given: Speed of light in glass = 1.91 x 108 m/s Speed of light in vacuum = 3.00 x 108 m/s = 3.00 x 108 m/s 1.91 x 108 m/s = 1.57 The refractive index is 1.57

Given: Refractive index in water = 1.33 Speed of light in a vacuum = 3.00 x 108 m/s 1.33 = 3.00 x 108 m/s v v = 2.26 x 108 m/s The speed of light in water is 2.26 x 108 m/s

How Light Refracts The part of the light beam that hits the medium first will slow down first

Angle of Refraction The angle of refraction is measured relative to the normal low refractive index (e.g. air)  high refractive index (e.g. glass) Light bends towards the normal

Angle of Refraction high refractive index (e.g. glass)  low refractive index (e.g. air) Light bends away from the normal

Dispersion The amount of refraction is different for each colour A single beam of white light can be split into a rainbow of colours Dispersion = the refraction of white light into separate wavelengths (colours)

Rainbows

Rainbows