1v=1f−1u\; \frac{1}{v} = \frac{1}{f} - \frac{1}{u}v1=f1−u1
= 110−12=120\; \frac{1}{10} - \frac{1}{2} = \frac{1}{20}101−21=201
v = 20
= 20 × 2.5 20\; \frac{20 \; \times \; 2.5 \;}{20}2020×2.5
= 2.5cm
