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