Sorry for the loose title but the question is based on a bad memory. The story goes like this: Many years ago I took an electrodynamics course and as far as I remember the profesor brought a special crystal to one lesson. The thing about this crystal that looked like a cube was that when held at a short distance from the table and illuminated from the side with a red laser the light was bent 90 degrees, exited the crystal through the bottom plane and illuminated the table. The special thing about it was that when you rotated the crystal 90 degree around any axis the laser was always directed down to the table.
I told this story to a friend who was taking the course a few years later and he asked the profesor about it, the profesor said he had no such device and couldnt remember the event.
Is this possible or just my brain mixing-up memories? What is the physical explanations behind it?
Thanks!
