A thin lens is placed 50cm from an illustrated object. The image produced has linear magnification of \(\frac{1}{4}\). Calculate the power of the lens in dioptres
- 2.5D
- 5.0D
-
10.0D
- 25.0D
The correct answer is: C
Explanation
\(\frac{1}{v} = \frac{1}{u}\)m = \(\frac{v}{u} = \frac{1}{4} = \frac{v}{50}\)
v = 12.5
But \(\frac{1}{v} + \frac{i}{u} = \frac{1}{f}\)
= \(\frac{1}{50} + \frac{1}{12.5} = f\)
f = 10m
P = \(\frac{100}{10} = 10D\)