In the given figure 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. 10cm
B. 15cm
C. 50cm
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)`
`(1)/(v)-(3//2)/(-20)=(1-3//2)/(20)rArr v=-10`
i.e. 10cm below the curved surface or 10cm above the actual position of flower.