Light incident normally on a plane mirror attached to a galvanometer coil retraces backwards as shown in Fig. 9.11. 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 ?

Light incident normally on a plane mirror attached to a galvanometer c

1.	Light incident normally on a plane mirror attached to a galvanometer coil retraces backwards as shown in Fig. 9.11. 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 ?
Answer» Solution :We know that in a plane mirror if for a GIVEN INCIDENT ray the pjg 911 mirror is rotated by an angle 0 then the reflected rays rotates in the same direction by an angle 20. It is given that on PASSING current mirror produces a deflection of 3.5°, hence the reflected ray rotates by 2 x 3.5° = 7°. `THEREFORE tan 7^(@) = d/(1.5 m) rArr d = 1.5 tan 7^(@) = 1.5 xx 0.1228 = 0.184 m = 18.4` cm

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Light incident normally on a plane mirror attached to a galvanometer coil retraces backwards as shown in Fig. 9.11. 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 ?

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