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    				| 1. | Light incident normally on a plane mirror attached to a galvanometer coil retraces backwards a shown in Fig. 6(a). 14. A current in the coil produces a deflection of `3.5^(@)` in the mirror. What is the displacement of the reflected spot of light on a screen placed `1.5 m` away ? | 
| Answer» Angle of deflection, `theta=3.5^(@)` Distance of the screen from the mirror, D=1.5m The reflected rays get deflected by an amount twice the angle of deflection i.e. 20= `7.0^(@)`. the displacement d) of the reflected spot of ligh on the screen is given as: `tan2theta=d/1.5` `therefore d=1.5 xx tan7^(@)` = 0.184 m =18.4 cm Hence, the displacement of the reflected spot of light is 18.4 cm. | |