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An object is placed at a distance of 40 cm from a concave mirror of focal length 15 cm. If the object is displaced through a distance of 20 cm towards the mirror, the displacement of the image will be |
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Answer» 36 CM towards the mirror  `(1)/(v_1)=1/f-(1)/(u_1)=(u_1-f)/(u_1f)` `therefore v_1=(u_1f)/(u_1-f)=((-40)(-15))/(-40-(-15))` `therefore v_1=(600)/(-25)=-24` cm Now `u_2`=-20 cm ,`v_2=?`  `(1)/(v_2)=(1)/(f.)-(1)/(u_2)=(u_2-f)/(u_2f)` `therefore v_2=(u_2f)/(u_2-f)=((-20)(-15))/(-20-(-15))` `therefore v_2=(300)/(-5)=-60` cm Distance between images = `v_2-v_1` =-60+24 =-36 cm As distance is POSITIVE hence 36 cm away from mirror. |
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