If the speed of light in air is represented by e and the speed in a medium is u, then the refractive index of the medium can be calculated using the formula_______.

The correct answer is e/u.

• When a light ray travels from one medium to another the speed of the light in each medium changes.

Key Points

• The degree to which a change in the direction of light in the two mediums is seen is called a refractive index.
• This means it is the measure of how much the light is bending while travelling from one medium to another.
• In its formula the refractive index is represented as ‘n’, the velocity of light in a vacuum is represented by ‘e’, and the velocity of light in a medium is ‘u'.
• Then n= e/u.

Additional Information

• The speed of light in vacuum c = 2.9972458 × 108 m/s ≈ 3.00 × 108 m/s. Index of refraction n=cv n = c v,
  • where v is the speed of light in the material, c is the speed of light in vacuum, and n is the index of refraction. Snell's law, the law of refraction, is stated in equation form as n1 sin θ1 = n2 sinθ2.