Question

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?

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

Answer 1

The correct option is A $10cm$

Considering refraction from a curved spherical surface at the air-concave surface interface,

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

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

Hence, $v=-10cm$

So the image appears to be 10 cm above the actual position.