A plane beam of natural light with intensity `I_(0)` falls on the surface of water at the Brewster angle. A fraction `rho = 0.039` of luminous flux is reflected. Find the intensity of the refracted beam.

Explanation

The enegry transmitted is, by conservation of enegry, the difference between incident energy and the reflected enegry. However the intensity is affected by the change of the cross section of the beam by refraction. Let `A_(i),A_(r ),A_(t)` be the cross sections of the incident, reflected and transmitted beams. Then
`A_(i) =A_(r)`
`A_(t) = A_(i)(cos r)/(cos i)`
But at Brewster's angle `r = 90-i`
so `A_(t) = A_(i) tani = nA_(i)`
Thus `I_(t) ((1-rho)I_(0))/(n)`