Unpolarized Light Intensity problem

[hardwork]

Homework Statement

Unpolarized light has intensity 15W/m^2 and is incident on a sheet of polarizing material whose transmission axis makes an angle of 25 degrees with the vertical. A second polarizer, whose transmission axis is horizontal, is located just past the first.

(a) What is the intensity of the light after it is transmitted through the first polarizer?
(b) What is the intensity of the light after it is transmitted through the second polarizer?

Homework Equations

I = (1/2)Io
I = Io(cos theta)^2

The Attempt at a Solution

a) I = (1/2)(15W/m^2) = 7.5W/m^2 -- haha sorry. I had it set up differently before, and put in the wrong answer.

b) How would I set this up? Would the angle be 90-25?

 

[Doc Al]

a) I = (1/2)(15W/m^2) = 30W/m^2

Check that arithmetic.

b) How would I set this up? Would the angle be 90-25?

Yes. So by what additional factor would the intensity be reduced?

 

[hardwork]

b) I = (7.5W/m^2)(cos 65)^2 = 1.3 W/m^2

Thank you for your help today!

 

[Doc Al]

b) I = (7.5W/m^2)(cos 65)^2 = 1.3 W/m^2

Looks good. (And you're welcome.)