# How can I compute the intensity of a polarized wave going through a Polaroid?

##### 1 Answer

You could use Malus' Law.

Malus' Law tells us that if you have a polarized wave (of intensity

Or:

Sounds difficult but look at the picture:

Knowing the angle

**Special case** :

When you have unpolarized light falling upon the polarizer the transmitted intensity will be

(to understand this, look at the mathematical explanation that follows and remember that the average value of

As a **mathematical explanation** you have:

If

The electric field vector

The analyzer will transmit only the component ( i.e

But intensity is proportional to the square of the electric vector you have:

and finally: