Question

What is relative shift of focal length of a lens when optical power is increased from 0.1 D to 2.5 D

(1) \(\frac{24}{25}\)

(2) \(\frac{13}{10}\)

(3) \(\frac{21}{15}\)

(4) \(\frac{11}{10}\)

Answer 1

Correct option is : (1) \(\frac{24}{25}\)

\(f = \frac{1}{p}\)

So, \(f_1 = 10\ m = \frac{1}{p_1}\)

And \(f_2 = \frac{1}{p_2} = \frac{10}{25}m\)

So \(\frac{|\Delta f|}{f_1} = \frac{24}{25}\)