1. The problem statement, all variables and given/known data The light beam travels from air into water,the angle of incidence is 60 degress. The bent beam creates point F on the bottom of eater tank.If we imagine extension of incident beam inside the water, we obtain point B on the bottom of water tank. The distance between F and B is 1m. Calculate the depth of the water. http://[url=http://postimg.org/image/rw3c1zipn/][PLAIN]http://s33.postimg.org/rw3c1zipn/bilde.jpg [Broken] 2. Relevant equations 3. The attempt at a solution First i used the Snells law to obtain the angle of the bent beam. Second i thought i use trigonometric functions to obtain the height. tg(angle1)=x/h and tg(angle2)=(x+1)/h From which I obtained negative value of x, which confused me. So guys, do you think this is the way to go or someone has any different ideas?