Concepts of Physics

IIT JEE Physics (1978-2018: 41 Years) Topic-wise Complete Solutions

Photography with and without polarizer

Introduction

When an unpolarized light is reflected from a surface, it gets partially polarized. If the angles are properly adjusted, the reflected light may become highly polarized. This experiment demonstrates this effect and uses it in a practical situation.

Apparatus

A glass plate, a camera (mobile Camera), a polarizer sheet.

Procedure

  1. Go to a place outdoor where sun is shining on some plants or soil.
  2. Place the glass plate so that the plants are behind the plate and sun falls on the plate at an angle of about 50 degree-60 degree with the normal.
  3. Put the camera to receive the reflected sunlight. Click photo. You will get a blot of sunlight and the plants behind will not be visible clearly.
  4. With the same position/orientation of the camera, put the polarizer sheet in front of the camera lens. Rotate the sheet in its own plane till you get best image of plants on the screen. Click the photo.
  5. Compare the two photos by looking them one after the other. You see that the plants are much more clearly visible when you use polarizer.

Discussion

The sunlight that is reflected from the glass plate gets polarised. By properly orienting the polarizer sheet, this polarized light can be stopped by the sheet. Thus the camera lens gets much less reflected sunlight and light coming from the plant through the glass plate gives good image. It is a regular practice in professional photographers to use polarizer filters. Polarizing sunglasses work on the same principle.