Question

At what angle above the horizontal is the sun if sunlight reflected from the surface of a calm lake is completely polarized? 

 What is the plane of the electric-field vector in the reflected light? 

• The plane of the electric-field vector in the reflected light is vertical and perpendicular to the plane of the page. 

• The plane of the electric-field vector in the reflected light is horizontal.

Answer 1

Part A

If is the Brewster's angle (the angle at which the reflected wave is polarised) and is the refractive index then we have

.

The angle above the horizontal is

Part B

The electric electric field vector of the reflected light is perpendicular to the plane of incidence and parallel to the plane of the surface from which it is reflecting. Hence the plane of electric field vector is horizontal.