Let there be two polaroids P 1 and P 2 . If the pass axis of P 2 makes an angle θ with the pass axis of P 1 , then when the polarised beam passes through the polaroid P 2, the component of electric field E cos θ along the pass-axis of P 2 will pass through P 2 . Thus, if we rotate the polaroid P 1 or P 2, the intensity of light will vary as: I = I 0 cos 2 θ Where I 0 is the intensity of polarised light after passing through P 1 . This is known as Malus' law.

How do you determine the resolving power of your eye?

We may perform a simple experiment to determine the resolving power of eye. We will make a pattern of black stripes of equal width separated by white stripes as shown in the figure below. All the black stripes should be of equal width, while the width of white stripes should increase from left to right. We have to paste the pattern at the height of our eye. By moving away or closer to the wall, we will find the position where we can see some two black stripes as separate stripes. ALL the black stripes which are left to it would merge into one another and on the right they would be more clearly visible. Note the width of the white stripe d that separates the two regions and measure the distance D of the eye from the wall. Then d D is the resolving power of our eye.