The Total solution for NCERT class 6-12
In the given figure, PQand RS are two mirrors placed parallel to each other. An incident ray ABstrikes the mirror PQ at B, the reflected ray moves along the path BC andstrikes the mirror RS at C and again reflects back along CD. Prove that AB ||CD.
Let us draw BM ⊥ PQ and CN ⊥ RS.
As PQ ||RS,
Therefore,BM || CN
Thus, BMand CN are two parallel lines and a transversal line BC cuts them at B and Crespectively.
∴∠2 = ∠3 (Alternate interior angles)
However, ∠1 = ∠2 and ∠3 = ∠4 (By laws of reflection)
∴ ∠1 = ∠2 = ∠3 = ∠4
Also, ∠1 + ∠2 = ∠3 + ∠4
∠ABC = ∠DCB
However,these are alternate interior angles.