Find % Light Through 3 Polarizers

[ScrubTier]

Homework Statement

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?

Homework Equations

I=I(nought) * cos^2 (theta)

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

 

[DrClaude]

2. 50*cos^2(90-Angle given)= x

Can you explain your thinking here?

 

[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.

 

[DrClaude]

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

 

[ScrubTier]

Would it just be angel given then?

 

[ScrubTier]

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

 

[DrClaude]

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

I would have said "distracted"

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