Concepts of Physics

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

Polarization Behavior of Cellophane Tape

Introduction

Cellophane is one of the most widely used material by all kinds of people. It has very interesting optical properties which are often not explored. In this experiment you will look at some of these properties related to polarization of light.

Apparatus

A few glass slides. Cellophane tape, a pair of polarizers, a marker pen.

Procedure

Peel off a strip of tape and paste it on a glass slide. Mark it as (1). Keep the two polarizers one above the other in parallel orientation. Look at the light source such as tube light/CFL/LED bulb. You see the light coming out clearly.

  1. Now put the glass slide between the two polarizers with edges of the slide parallel to those of the sheets. Call it \(\theta=0\). How does the tape portion look like?
  2. Now rotate the glass slide slowly, keeping it between the two parallel polarizing sheets. Roughly estimate \(\theta\) and for each \(\theta\), write in table, how the tape looks like? Go for \(\theta=0\degree\) to 180\degree.
  3. Take a fresh slide ad paste two layers of Cellophane tape on the same slide, parallel to each other. Mark the slide as (2). Repeat steps, 1-2 and write your observations in table.
  4. Take a fresh slide. Paste one layer of tape on this. Paste another layer of tape perpendicular to the first layer. Mark the slide as (3). Repeat steps 1-2 and write your observation in table.
  5. Now put the two polarizing sheets one above the other in crossed orientation. Look at a light source and make sure that almost no light comes in. Now place slides (1), (2) and (3) one by one and repeat steps. 1-2 for each.
  6. Do whatever you design.
  7. Write conclusions from all these observation.

Note

Tables to be made