Question

Two objects A and B when placed one after another infront of a concave mirror of focal length 10 cm from images of same size. Size of object A is four times that of B. If object A is placed at a distance of 50 cm from the mirror, what should be the distance of B from the mirror

• A. 10 cm
• B. 20 cm
• C. 30 cm
• D. 40 cm

Answer 1

Answer: (B)

20 cm

Answer 2

By using $\Rightarrow \frac { 1 } { 1 } \times \frac { 1 } { 4 } = \frac { - 10 - u _ { B } } { - 10 - ( - 50 ) }$ $\Rightarrow$ $u _ { B } = - 20 \mathrm {~cm}$ .