Laws of Reflection

Double glazing, an opposing pair of windows, and bright Christmas lights combine give rise to multiple images.

The view is almost that of a kaleidoscope, and the images and their relative positions keep changing as the observer moves around. The effect is really lovely in a darkened room.

This photograph is (pretty obviously!) of the end where we have put our Christmas tree. The primary reflections are of

a lighted spiral "tree" and of "icicle" lights shown in this link.

at the opposite end of the room. But you can readily make out the secondary reflection of the reflection of the lighted tree at this end. The human observer, whose eyes have (much) greater sensitivity and dynamic range than the camera, can see several higher-order reflections. (You can just make one out on the extreme left here.)

If you lined everything up carefully, you just might make a laser if only the lights were the right kind. I doubt it VERY much, though... Christmas phun for a physicist!