Ncert Exercises & Solutions

Can reflection result in a plane polarised light if the light is incident on the interface from the side with a higher refractive index?

Hint: The polarization of light depends on the angle of incidence.

Step 1: Find Brewster's angle.

When the angle of incidence is equal to Brewster's angle, the plane transmitted light is unpolarised and reflected light is plane polarised.

Consider the diagram in which unpolarised light is represented by dot and plane polarised light is represented by arrows.

Polarisation by reflection occurs when the angle of incidence is equal to Brewster's angle.

i.e., tan $i_{B} = μ_{21} = \frac{μ_{2}}{μ_{1}} w h e r e μ_{2} < μ_{1}$

Step 2: Find the critical angle.

When the light rays travel in such a medium, the critical angle is;

$\sin i_{c} = \frac{μ_{2}}{μ_{1}}$ where $μ_{2} < μ_{1}$
As $As | \tan i_{B} | > | \sin i_{C}$ for large angles $i_{B} < i_{C .}$
Thus, the polarisation by reflection occurs definitely.

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