Cause of Refraction
The speed of light is different i. n different media.
Laws of Refraction
( i) The incident ray, the refracted ray and the normal at the point of incidence, all three lies in the same plane.
( ii) The ratio of sine of angle of incidence to the sine of angle of refraction is constant for a pair of two media,
where 1 & mu 2 is called refractive index of second medium with respect to first medium.
This law is also called Snell’ s law.
Refractive Index
The ratio of speed of light in vacuum( c) to the speed of light in any medium( u) is called refractive index of the medium.
Refractive index of a medium, μ = c / v Refractive index of water = 4 / 3 = 1.33; Refractive index of glass = 3 / 2 = 1.50
When light is reflected by a denser medium, phase difference of π radian or path difference of λ / 2 or time difference T / 2 is produced. This is known as Stoke’ s law. Distance x travelled by light in a medium of refractive index μ is equal to distance(& mux) travelled in vacuum.
Time taken by light to traverse a thickness x of time = μx / c, where c = velocity of light in vacuum. Relative Refractive Index The refractive index of second medium with respect to first medium