Question

in the given figure, two plane mirrors OM and ON are
inclined at an angle 0. A light ray AB falls on mirror OM
and makes 40° angle with the normal BC is the
reflected ray which falls on mirror ON and makes 30"
angle with the normal. Find value of o.
(A) 70
(B) 60°
(C) 50°
(D) 80°
​

Answer 1

Answer:

A) 70°

Explanation:

This requires Laws of Reflection and a bit of Math.

Let the normals be PB and QC.

Angle of incidence = Angle of reflection

PBC = ABP = 40°

Now, CBO = 90° - PBC = 90° - 40° = 50°

And, BCO = 90° - QCB = 90° - 30° = 60°

Using Angle Sum Property,

θ + 50° + 60° = 180°

θ = 180° - 110° = 70°