Two plane mirrors are inclined at 70°. A ray incident on one mirror at angle θ, after reflection falls on the second mirror and is reflected from there parallel to the first mirror. The value of θ is:
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Question

Two plane mirrors are inclined at 70°. A ray incident on one mirror at angle θ, after reflection falls on the second mirror and is reflected from there parallel to the first mirror. The value of θ is:

Options

G1 Physics · Accepted Answer

Step 1: At each mirror the angle of incidence equals the angle of reflection. Step 2: Draw the two mirrors with included angle 70° and the final ray parallel to the first mirror. Step 3: From the reflected-ray geometry, θ + 40° = 90°. Step 4: Thus θ = 50°. Final answer: (D) 50°.