How do two aligned Polaroids transmit light in Grade 12 physics problems?

[moonpearl]

Grade 12 physics problems :(

One question:

Because of absorption, a Polaroid will actually transmit 40% of nonpolarized light incident on it. Two such Polaroids with their axes aligned will transmit
a. 16%.
b. 24%.
c. 30%.
d. 32%.
e. 40%.

The answer is 32% and I have no cue why. My textbook doesn't say anything and since I am taking a conceptual physics course, I have no formulas to work with. Does anyone know why this is the answer?

Thanks,
LA

 

[Galileo]

An ideal polarizer will let 50% of the unpolarized light through.
These polarizers in the problem are not ideal, they absorb a fraction/percentage of the light they should let through. Can you find this fraction to be 0.8?

After that, since the light which went through the first polarizer is now linearly polarized in the direction of the second polarizer, the second polarizer should let all light through if it was ideal. But it again stops 80% if the light which is incident upon it.

 

[wais]

Hi LA, understanding polarization can be a challenging concept in physics. In this case, the answer can be found by applying Malus' Law, which states that the intensity of light transmitted through two polarizing filters is equal to the intensity of the incident light times the cosine squared of the angle between the filters. In this problem, the angle between the two polarizing filters is 0 degrees (since their axes are aligned), so the cosine of 0 degrees is 1. Plugging this into the equation, we get: I = (40%)(1^2) = 40%. However, the question is asking for the percentage of nonpolarized light transmitted, so we need to multiply this by 100% - which gives us 40% x 100% = 40%. Therefore, the correct answer is 40% x 40% = 16%, which is option a. Hope this helps clarify the solution for you. Keep up the good work in your conceptual physics course!