The power and aperture of lenses $L_1, L_2$ and $L_3$ are given below in tabular format. Which pair of lenses should be chosen for constructing a microscope?

$L_2$ as eyepiece and $L_3$ as objective

The correct answer is Option (1) → $L_2$ as eyepiece and $L_3$ as objective

Objective lens should have high power and small focal length, eyepiece should have lower power and larger aperture.

Given:

L1: Power = 3 D, Aperture = 8 cm

L2: Power = 6 D, Aperture = 1 cm

L3: Power = 10 D, Aperture = 1 cm

Focal length: f = \frac{100}{P} (cm, P in D)

$f_{L1} = \frac{100}{3} \approx 33.33 \text{ cm}$

$f_{L2} = \frac{100}{6} \approx 16.67 \text{ cm}$

$f_{L3} = \frac{100}{10} = 10 \text{ cm}$

Objective: L3 (shortest focal length)

Eyepiece: L2 (longer focal length, suitable aperture)

Answer: L2 as eyepiece and L3 as objective.