A plano-concave lens is placed on a paper on which a flower is drawn. How far above its actual position does the flower appear to be?

Options

A. 10 cm
B. 15 cm
C. 50 cm
D. none of these

Answer

A

Explanation

Considering refraction at the curved surface,
`u=-20 , mu_(2)=1`
`mu_(1)=3//2, R=+20`
applying `(mu_(2))/v-(mu_(1))/u=(mu_(2)-mu_(1))/R`
`rArr 1/v-(3//2)/(-20)=(1-3//2)/20 rArr v=-10`
i.e., 10 cm below the curved surface or 10cm above the actual position of flower.