A ray travels in the direction 3î − 4ĵ and strikes a plane mirror whose surface is parallel to the x-axis. Which vector is parallel to the reflected ray?
Physics · Geometrical optics · law of reflection and plane mirror
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Question

A ray travels in the direction 3î − 4ĵ and strikes a plane mirror whose surface is parallel to the x-axis. Which vector is parallel to the reflected ray?

G1 Physics · Accepted Answer

Reflection at a horizontal mirror reverses only the component normal to the mirror. The x-component remains 3 and the y-component changes from −4 to +4. Hence the reflected direction is 3î + 4ĵ.