Refraction

Created by

Eva

Cards (9)

Refraction
The bending of waves as they pass through a different medium. This occurs because they travel at different speeds in different materials
Light waves travel more slowly through denser substances
Light travels at around 300 million m/s through air
Light slows to around 200 million m/s through glass
When light passes through a denser material, it bends towards the normal
Angle becomes bigger
When light passes through a less dense material, it bends away from the normal
Angle becomes smaller
Prisms
When white light is shone through a prism, it will split into different colours
because white light is a mixture of various frequencies of visible light
The Refractive Index
All transparent materials have a refractive index (n)
Reveals how quickly light is travelling through that particular material
Snell's law:
n = Sin I / Sin R n = refractive index i = angle of incidence r = angle of refraction
Light, Reflection and Refraction
The refraction of light can be investigated using a ray box
Place a rectangular glass block on a piece of paper
using a pencil, draw the normal (perpendicular to block)
Shine a light ray through the block
Trace the incident and emergent rays on the paper
Join the lines together to create a refracted ray
calculate the angles of incidence and refraction
The angle of incidence should be greater than the angle of refraction
Total Internal Reflection
When light waves move from a denser material to a less dense material, all of the light can be reflected
Referred to as total internal reflection (TIR)
TIR occurs when the angle of incidence exceeds the critical angle (c)
Past a certain angle, all of the light waves will be reflected
In glass, c is around 42°
Critical Angles and the Refractive Index
There is a relationship between c and the refractive index
The higher the refractive index, the lower the critical angle
sinc = 1/n c = critical angle (°) n = refractive index