9.37:
Light incident normally on a plane mirror attached to a galvanometer coil retraces backwards as shown in Fig. 9.36. A current in the coil produces a deflection of 3.5° of the mirror. What is the displacement of the reflected spot of light on a screen placed 1.5 m away?
Hint: The deflection experienced by the reflected rays = twice the angle rotated by the mirror.
Step 1: Find the deflection experienced by the reflected rays.
The angle of deflection, θ=3.5°
The distance of the screen from the mirror, D=1.5 m
The deflection experienced by the reflected rays = twice the angle of deflection = 2θ = 7.0°
Step 2: Find the displacement of the refracted spot of light.
Following displacement (d) of the reflected spot of light on the screen:
Hence, 18.4 cm is the displacement of the refracted spot of light.
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