Is the Amplitude Halved After Light Passes Through a Polarizer?

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SUMMARY

The discussion clarifies that the amplitude of light is not halved after passing through a polarizer; instead, the focus should be on irradiance. When natural light with a flux density I0 passes through HN-38 and then HN-32, which is oriented at a 30-degree angle to the first, the irradiance after the second polarizer will be less than half of the incident light due to the properties of real polarizers. The ideal assumption of halving the amplitude applies only to theoretical scenarios, not practical applications involving specific polarizing materials.

PREREQUISITES
  • Understanding of light properties, specifically irradiance and amplitude.
  • Familiarity with polarizers, particularly HN-38 and HN-32 materials.
  • Knowledge of the mathematical relationships governing light transmission through polarizers.
  • Basic principles of optics, including the effects of angles on light transmission.
NEXT STEPS
  • Research the transmission characteristics of HN-38 and HN-32 polarizers.
  • Study the mathematical derivation of light irradiance through multiple polarizers.
  • Learn about the differences between ideal and real polarizers in optical applications.
  • Explore the implications of light polarization in practical scenarios, such as photography and LCD technology.
USEFUL FOR

Students in optics courses, physics educators, and professionals working with optical devices who need a deeper understanding of light behavior through polarizers.

Shackleford
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Whenever there is natural light, you always assume the amplitude is 1/2 of the incident light amplitude after the first polarizer, right?

http://i111.photobucket.com/albums/n149/camarolt4z28/a1.png

http://i111.photobucket.com/albums/n149/camarolt4z28/IMG_20111030_161325.jpg
 
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Shackleford said:
Whenever there is natural light, you always assume the amplitude is 1/2 of the incident light amplitude after the first polarizer, right?
No. Don't worry about amplitude, just work with the irradiance -- which is different than amplitude.

http://i111.photobucket.com/albums/n149/camarolt4z28/a1.png

http://i111.photobucket.com/albums/n149/camarolt4z28/IMG_20111030_161325.jpg
If I may requote the stated problem, it will be easier for us to follow what is going on:
Natural light having a flux density I0 is incident on a sheet of HN-38. After the light passes through the sheet of HN-38, it transmits through a sheet of HN-32 whose axis of transmission makes an angle of 30 degrees with respect to the transmission axis of the first sheet. Find an expression for the irradiance of the beam after it emerges from the second polarizer.
In an ideal polarizer, the irradiance of natural light is 1/2 after transmission through it. However, for real polarizers HN-38 and HN-32, the irradiance will be less than 1/2.

If your professor wants you to use the actual transmissions of HN-38 and HN-32, then that information should have been provided to you somehow -- either in your lecture notes, class handouts, course website, textbook, or somewhere in the problem set you have been given.

(And if your professor wants you to use the transmission of an ideal polarizer, then I don't think he would have specified two different polarizing materials.)
 
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