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An object is placed at 20 cm from the pole of a concave mirror. It forms real image at a distance of 60 cm from the pole. Find the focal length of the concave mirror. |
Answer» In the given problem, Object distance, u = - 20 cm (using Cartesian sign convention ) image distance , v =- 60 cm (using Cartesian sign convention for real image) Focal length of the mirror is given by, `1/f = 1/u + 1/v` `1 /f=(-1)/20 + (-1)/60` `1/f = (-(60+20))/(60 xx 20) (-80)/(1200)` ` f = (-1200)/80 =- 15` cm The focal length of the given concave mirror is 15 cm. |
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