In Fig. 6.33, 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. Prove that AB || CD.

Explanation

1) PQ||PS

2)BE`_|_`PQ and CF`_|_`RS

`angle1=angle2 and angle3=angle4`

angle of incidence is equal to angle of reflection.

PQ||RS and BF and C for`_|_`

`angle2=angle3`(alternate angles)

from equation (1) and (2)

`angle1=angle3`

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