The reecting surfaces of two mirrors form a vertex with an angle of 120. If a ray of light strikes mirror 1 with an angle of incidence of 55, nd the angle of reection of the ray when it leaves mirror 2.

Modern Physics Lecture 1: Foundations and Special Relativity Position, Time, and Rotation are all continuous symmetries (discrete symmetries such as reflection do not produce the same results as below): Invariance in position (changing where in space you perform your experiment) proves momentum conservation Invariance in rotation (eg. rotating your entire experiment by 90 degrees) proves conservation of angular momentum Invariance in time (changing when in time you perform your experiment, eg. today vs. tomorrow) proves energy conservation Newtonian Mechanics: Inertia F=ma The force of object 1 on object 2 is equal in magnitude to the force of object 2 on object 1 True in an inertial reference frame