# Homework Help: Three polarizers

Tags:
1. Apr 4, 2016

### ScrubTier

1. The problem statement, all variables and given/known data

Polarizers 1 and 3 have their axes of polarization, indicated by the black solid lines, perpendicular to each other. If you try to shine light through only the combination of 1 and 3, you will find that none passes through. However, now we put in another polarizer (number 2 in the figure) between number 1 and number 3. This polarizer has an axes of polarization that has an angle of θ = 42° with respect to the polarization axes of polarizer 1. Surprisingly, now some light passes through the combination 1+2+3. What percentage of the initial (unpolarized) light intensity passes through?

2. Relevant equations
I=I(nought) * cos^2 (theta)

3. The attempt at a solution
1. 100/2 = 50
2. 50*cos^2(90-Angle given)= x
3. x*cos^2 ((90-angle given)-angle given)= Answer

2. Apr 4, 2016

### Staff: Mentor

Can you explain your thinking here?

3. Apr 4, 2016

### ScrubTier

We had had a similar problem but using only two polarizers so I was thinking after the first one the same ideas could be applied for the last two.

4. Apr 4, 2016

### Staff: Mentor

I don't understand why you take "90 - Angle given".

5. Apr 4, 2016

### ScrubTier

Would it just be angel given then?

6. Apr 4, 2016

### ScrubTier

Okay you pointing out how stupid I was being really helped, I got it! Thank you

7. Apr 4, 2016

### Staff: Mentor

I would have said "distracted"

Be careful when using solutions from other problems that you are applying them correctly for the problem at hand.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted