Question

for a coverging lens,the object distance is 25cm and image distance is 50cm what is the focal lens of the lens.​

Answer 1

Given that:

• Object Distance is 25 cm
• Image distance is 50 cm.

Need to find:

• The focal length of the lens= ?

Solution:

The formula of focal length is —

${\qquad}{\bigstar{\boxed{\sf{ \frac{1}{f} = \frac{1}{v} - \frac{ 1}{u}}}}}$

According to the question —

$\sf \implies \: \frac{1}{f} = \frac{1}{ - 50} - \frac{1}{ - 25} \\ \\ \sf \implies \: \frac{1}{f} = \frac{1 - 2}{ -50} \\ \\ \sf \implies \: \frac{1}{f} = \frac{ - 1}{ - 50} \\ \\ \sf \implies \: \frac{1}{f} = \frac{1}{50} \\ \\ \sf \implies \: f = 50 cm$

Hence,focal length of the lens is 50cm.