How Does Light Intensity Change Through Multiple Polarizers?

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Homework Help Overview

The discussion revolves around the change in light intensity as it passes through multiple polarizers, specifically focusing on the application of the equation Itrans = I0 Cos2θ. Participants are examining how to correctly apply angles for polarized light and the resulting intensity calculations.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the application of the intensity equation for polarized light, with varying interpretations of the angles used for calculations. Some question the choice of angles for the second polarizer and whether to use the initial angle or the angle relative to the first polarizer.

Discussion Status

The discussion is ongoing, with participants sharing their calculations and interpretations. Some express agreement with specific approaches, while others seek clarification on the reasoning behind angle choices. There is no explicit consensus on the correct answer, but multiple interpretations are being explored.

Contextual Notes

Participants note the importance of understanding the orientation of the polarizers and the implications of using different angles in calculations. There is mention of differing answers from other sources, indicating potential confusion in the problem setup.

Sgtsloth
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So I know the equation:

Itrans = I0 Cos2θ

Since this light starts out as polarized, there is no need to cut it in half like you do for unpolarized light. So I did the equation through the first polzarizer, using 30 degree as my angle, and came out with I=0.75

Now I used that 0.75 as my new I0 as the light went through the 2nd polarizer, this time I used 60 degrees as my θ and I got 0.1875, which would be B.

However, I saw the same problem elsewhere where the guy got D) as the answer because he used 30 for θ instead of 60.
 
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I agree with you.
 
edit: I didnt notice the opposite axis of the second one, I would say you are correct in your first assumption and I agree with the rest of the posters. use 30 then 60
 
Last edited:
Pharrett said:
Since you have 2 polarized sheets at 30 degree I would use 1(cos30^2)^2

That gives 0.5625, can you explain WHY you would use 30 degree for the second polarizer when the axis is 60 after the coming out of the first one?
 
Anyone else want to chime in, I still don't know which is correct.
 
Sgtsloth said:
Anyone else want to chime in, I still don't know which is correct.
B is the right answer. Your analysis of using 30 then 60 degrees is correct.
 
TSny said:
B is the right answer. Your analysis of using 30 then 60 degrees is correct.
Thank you
 

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