Polar eyes
More on polarisation. This time thanks to Russel Fleming and his students (I think its about time my students spotted something). Looking in a mirror whilst wearing the sort of 3D glasses you wear in the cinema makes your eyes look weird. I tried this this morning and have been wondering about it all day. 3D cinema uses circularly polarised light, that's light where the amplitude of oscillation of the E field is constant but rotating. There are two directions of rotation, clockwise and anticlockwise. Clockwise can't go through an anti clock filter and visa verse. So the 3D projector projects two images one clockwise polarised the other anti clock, and the glasses have two different filters to separate the left and right eye images. Now, for reasons as yet unknown (to me that is) reflection changes the direction of polarisation so if you look at the mirror with the glasses on your right eye only sees the left and the left the right, thats what gives the strange effect. I tried shutting one eye and lo and behold could only see the one that was closed. In the photo the light from the camera can't pass back into the lens but light that has passed through the other lens can. Oh dear I've just given the game away. In a previous post I said I had Harry Potter 3D glasses but as you can see in the photo I haven't, they were more expensive than the ordinary ones. I think they look like Raybans.