Question

A pair of polarized sunglasses is created with the purpose of minimizing the intensity of reflected sunlight (glare) off of a horizontal water surface. The polarization axis for these sunglasses should be ________ and the effect will be most noticeable when the observer looks ____ below the horizontal. Water has an index of refraction of 1.33 and air has an index of 1.00. a) horizontal, 36.9° b) vertical, 36.9° c) vertical, 53.1° d) horizontal, 53.1° e) none of the above will minimize glare

Answer 1

Polarized sunglasses are generally used to block the glare which coming from the horizontal water surface. When large concentration of light gets aligned parallel to the water surface then its result is glare. To avoid this plane polarized light coming from horizontal surface, a filter with a vertically aligned polarization axis must be used. This vertical filter of tint allow vertically reflected light and block horizontally reflected light that is polarized glare.

In order to minimize the intensity of reflected sunlight or glare the polarizing lens should be positioned at a 90-degree angle to the source of the glare. At one particular angle of reflection light becomes completely polarized parallel to the surface and that angle is called Brewster’s angle. Brewster’s angle for water is 53 degrees.

We can calculate Brewster's angle as,

tan 0 =

                               where,

                                        is refractive index of water and air respectively.

1.33 ..tan =

.. = tan-11.33 = 53.1

So the answer is option:- c) vertical, 53.1 degree.

The polarization axis for these sunglasses should be vertical and the effect will be most noticeable when the observer looks 53.1 below the horizontal.