Question

If the power of a lens is + 0.1 D and if the object of size 2 cm is placed 5 cm before the lens. Find the size and position of the image formed.

• A. image size = 4 cm, image distance = – 10 cm
• B. image size = 10 cm, image distance = – 4 cm
• C. image size = 4 cm, image distance = 10 cm
• D. image size = 4 cm, image distance = 5 cm

Answer 1

The correct option is A

image size = 4 cm, image distance = – 10 cm

P = $\frac{1}{f}$ ⇒ f = 10 cm

$\frac{1}{v}$ - $\frac{1}{u}$ = $\frac{1}{f}$

$\frac{1}{v}$ - $\frac{1}{(-5)}$ = $\frac{1}{\left(10\right)}$

v = - 10 cm

$\frac{v}{u}$ = $\frac{h^{/}}{h}$ ⇒ $\frac{-10}{(-5)}$ = $\frac{h^{/}}{2}$

$h^{/}$ = 4 cm

Image height = 4 cm