A ray has unit direction (2î − 2ĵ + k̂)/3 and strikes a plane mirror whose unit normal is k̂. What is the reflected unit direction?

Question

G1 Physics · Accepted Answer

Using êᵣ=êᵢ−2(êᵢ·k̂)k̂, only the k̂ component reverses. Hence êᵣ=(2î−2ĵ−k̂)/3.