Question

Define refractive index . What are its units ???????What is the cause of dispersion????????  

Answer 1

Suppose light rays are traveling from medium 1 to 2. Let i be angle of incidence with the normal at the surface at the point of incidence .  let r be angle of refraction in the medium 2 with the normal.  Then

Mu = refractive index =  sin i / sin r

Mu = velocity light in vacuum / velocity of light in the medium

Refractive index is  dimensionless.

Dispersion is caused due to different angles of refraction for different colors (wavelengths ) of components of white light.  Violet has higher r , red color deviates least ie., r is the least.