A beam of unpolarised light is incident on the boundary between 2 transparent media if the reflected light is completely plane polarised, how is its direction related to the direction of corresponding refracted light?

When unpolarized light is incident on a transparent refracting medium, at a particular angle of incidence the reflected light and refracted light are perpendicular to each other that angle of incident is known as a polarizing angle.


Polarization of reflection, the reflected light gets completely plane-polarized and which makes an angle \(frac{pi }{2}\) with the refracting light.

According to brewster’s law,

ip + r = 90°

r – is angle of refraction

ip – is polarising angle

r = 90° – ip

by snell’s law

μ1 sin i = μ2 sin r

μ1 = 1 and μ2 = μ

\(frac{sin i}{sin }=mu\)


i = ip and

r = 90° – ip

\(frac{sin {{i}_{p}}}{sin (90{}^circ -{{i}_{p}})}=mu\) \(frac{sin {{i}_{p}}}{cos {{i}_{p}}}=mu\) \(tan {{i}_{p}}=mu\) This relation is known as Brewster angle.

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