Data: PQ and RS are two mirrors placed parallel to each other. An incident ray AB strikes the mirror PQ at B. the reflected ray moves along the path BC and strikes the mirror RS at C and again reflects back along CD.
To Prove : AB||CD.
Proof : PQ is a mirror. AB is a incident ray, BC is reflected ray. ZABC is angle of incidence. ∠BCD is angle of reflection.
Incident ray formed in PQ mirror is equal to reflected ray formed in RS mirror.
∴ ∠ABC = ∠BCD.
These are pair of alternate interior angles, then AB||CD.
