Question

In the given figure a piano-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 ?

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

Answer 1

The correct option is A 10 cm

Refraction occurs at curved surface.So,

$u=-20,{\mu }_2=1,{\mu }_1=\frac{3}{2},R=\pm 20$

Applying formula, we get

$\frac{{\mu }_2}{v}-\frac{{\mu }_1}{u}=\frac{{\mu }_2-{\mu }_1}{R}$

$\frac{1}{v}-\frac{3/2}{-20}=\frac{1-3/2}{20}$

$v=-10$

The position will be 10 cm below the curved surface or 10cm above the actual position of flower.