1. Two mirrors are placed parallel to each other on a sea-saw. A beam incident in analmost vertical plane, on the first mirror is reflected to be incident on the second and then is further reflected to form a spot on the wall at some distance away. If the sea-saw is turned through an angle theta, through what angle will the reflected beam turn? 2. If for two vectors A and B; |A+B|=|A-B| then a) |A-B|=|A|+|B| b) |A+B|=|A|-|B| c) |A+B|=0 d) |A.B|=0 Please let me explai, I have no idea about these questions. Please explain it to me. I have astonomy olympiad so I got them by reading the past papers.