Two plane mirrors are inclined to each other at an angle of 70o. A ray is incident on one mirror at an angle θ. The ray reflected from this mirror falls on the second mirror from where it is reflected parallel to the first mirror. What is the value of θ? 


Correct option is



A ray AB is incident at an angle θ on mirror M1 and is reflected along BCas shown in fig. The ray makes and angle γ with the normal CN2 and is reflected along CD making an equal angle γ with the normal. Since CD is parallel to mirror OM1.    


It is clear from the diagram that 







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