Question

Materials that rotate the plane of polarization of light are called "optically active". Try putting some or all of the following between two polarizers whose transmission axes are crossed: corn syrup, a plastic protractor, a piece of mica or other crystal. Explain what you see. Where do the colors come from?

Answer 1

Corn syrup- optically active made of helical sugar molecules and exhibits birefringence which causes substance to have more than one refractive index. When a white light is sent through polariser, various wavelengths of light produced can be seen on screen due to variable refractive index of the syrup medium.

Plastic protractor - probably immediately myriad(stresses of plastic) of colours can be seen. These can be made to change by rotating the polariser. Subjects that have this prooerpr of altering the direction of plane of polarization of an incident beam of light are called birefringent.

A piece of mica - mica acts to change the orientation of polarized light by 90 degrees. Place a thin sheet of mica between two polarizers that are 90 degrees to one another so that no light can pass through. Then, one can orientation the mica so that it rotates all of the polarized light coming through first polarizer to be oriented the same way as the second polarizer, to let light pass through it again.

Hope it sufficiently helps. Any queries are welcome!