You may recall the book problem where someone enters a room 15 feet wide with mirrors on the left and right walls. She stands five feet from say the left wall and faces it. The question is how far from her do the first three images of herself appear. Her first image appears to be 10 feet from her: 5 to the mirror and the image appears to be 5 feet behind the mirror. When I solved it for her second and third images I got 40 feet and 70 feet for the answers. This differed from the books answers of 30 feet and 40 feet for the second and third images. In all cases I was considering the image of her front.
A couple of students have suggested the following explanation. The second image is not of her front, but of her back! The image of her back must travel 10 feet to the right wall and then 15 feet to the the left wall so it appears to be 25 feet behind the left wall and thus 30 feet from her. The third image is of her front and corresponds to my second image.
In any case the images beyond the first would barley exist, since the girl's body would block most rays from the right mirror from reaching the left mirror and those from the left mirror from reaching the right mirror.
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