Why is polarized light used in microscopy for the analysis of rocks(for example)?
Why not use unpolarized light? What is it with polarized light that makes the analysis of rocks better?
Edit: please refer to the actual physics behind your answer
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asked Oct 31, 2015 at 20:09
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$\begingroup$ Birefringence is one good reason. $\endgroup$– Jon CusterCommented Oct 31, 2015 at 20:11
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$\begingroup$ What is birefringence? $\endgroup$– TheQuantumManCommented Oct 31, 2015 at 20:11
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1$\begingroup$ Wikipedia is your friend. But, the optical properties differ along different crystal axes, so the reflectivity changes with polarization. $\endgroup$– Jon CusterCommented Oct 31, 2015 at 20:13
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sometime it's difficult to isolate what you see from the background. It you use 2 cross polarizers, no light is supposed to pass through, which switch off the background. but if between the 2 polarizers your sample has any effect on polarization angle, then its light wont be cancelled, and it will appear luminous on a dark background.
Also, many colors will appear, since polarization shift will be different with frequency.
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$\begingroup$ Thank you for your reply, although my question was why not use unpolarized light. $\endgroup$ Commented Oct 31, 2015 at 20:17
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$\begingroup$ as I said, with unpolarized light, your object might look bright in the bright. also, many colors will appear. see google.fr/… $\endgroup$ Commented Oct 31, 2015 at 20:18