• When light?enters a?denser?medium?(such as glass) it slows down and?bends?towards?the normal
  • How much the light bends depends on the?density?of the material

   

Angle of incidence i and angle of refraction r through a glass block

• If light travels from a?less?dense to a?more?dense medium (e.g. air to glass),?r?< i?(bends towards the normal)
• If light travels from a?more?dense to a?less?dense medium (e.g. glass to air),?r?> i?(bends away from the normal)

• The angles of incidence and refraction are related by an equation known as?Snell's Law:

• Where:
  • n?= the refractive index of the material
  • i?= angle of incidence of the light (°)
  • r?= angle of refraction of the light (°)

   

• 'Sin' is the trigonometric function 'sine' which is on a scientific calculator

• This equation can be rearranged with the help of the formula triangle:

Snell's law formula triangle

• The refractive index is a number which is related to the speed of light in the material (which is?always less?than the speed of light in a vacuum):

• The refractive index is a number that is?always larger than 1?and is different for different materials
  • Objects which are more?optically dense?have a?higher?refractive index, eg.?n?is about 2.4 for diamond
  • Objects which are less?optically dense?have a?lower?refractive index, eg.?n?is about 1.5 for glass

   

• Since refractive index is a?ratio, it has?no units

Step 1: List the known quantities

• • Refractive index of glass, n = 1.53
  • Angle of incidence, i = 15°

   

Step 2: Write the equation for Snell's Law

Step 3: Rearrange the equation and calculate sin (r)

Step 4: Find the angle of refraction (r) by using the inverse sin function

r = sin^–1?(0.1692) = 9.7 =?10°