# Homework Help: Need help with question regarding polarization filters

1. Nov 17, 2015

### ZHIHUI

• Moved from a technical forum, so homework template missing
Un-polarized light is incident upon two polarization filters and do not have their transmission axes aligned. If 18% of the light passes through this combination of filters, what is the angle between the transmission axes of the filters.

I got 64 degrees using I = Imax(cosΦ)^2 but the correct answer is 53 degrees.

Thank you very much!!

2. Nov 17, 2015

### Staff: Mentor

What happens when the light hits the first filter?

3. Nov 17, 2015

### ZHIHUI

The light will be linearly polarized. If the first filter is ideal, intensity of the transmitted light will be exactly half that of the incident un-polarized light.

4. Nov 17, 2015

### Staff: Mentor

Correct. So how does that affect the terms in your equation?

5. Nov 17, 2015

### ZHIHUI

I got it!
Thank you very much!
Sorry for the trouble!

6. Nov 17, 2015

### Staff: Mentor

No trouble, that what PF is for!