Statement of Brewster's Law
Reason of different value
When unpolarised light is incident on the surface separating two media, the reflected light gets (completely) polarized only when the reflected light and refracted light become perpendicular to each other.
[ Alternatively:
If the student draws the diagram, as shown, and writes ip as the polarizing angle, award this 1 mark.
If the student just writes µ=tan‌ip, award half mark only.]
The refractive index of denser medium, with respect to rarer medium, is given by µ=tan‌ip Since Refractive index (µ) of a transparent medium is different for different colours, hence Brewster angle is different for different colours.