Birefringence physics question

I am struggling to interpret what is the polarisers' role in part b) of this question, part a inquired for the thickness of the prism:
https://isaacphysics.org/questions/birefringence?board=7cc30f8f-d6cc-48d1-9218-d0ba88e6caf0&stage=all
I would be grateful for any help

(edited 1 year ago)

Reply 1

mosaurlodon

Does this post help
https://www.thestudentroom.co.uk/showthread.php?t=6378758
tbh I also didnt really understand this question when I did it a long time ago so im gonna have another look at it now.

Reply 2

Eimmanuel

Study Forum Helper

Original post by Javier García

Just in case, you still want “an explanation”.

Your question is answered in the question itself.

“The light emerging from the first polariser is polarised at an angle of 45° to A and so can be considered to be made up of equal amplitudes of light with polarisation directions A and B defined above.”

Without the top polariser, you can watch the first video provided Isaac Physics from Sixty Symbols to see that there is a double-image or double vision when we view through a birefringence crystal.