The distance of distinct vision of a person is `50 cm`. He wants to read a book placed at `25 cm`. What should be the focal length of the spectacles ?

Answer

`+ 50 cm`

Explanation

Here, `u = -25 cm, v = - 50 cm`,
As `(1)/(f) = (1)/(v) - (1)/(u) = (1)/(-50) + (1)/(25) = (1)/(50)`
`:. f = + 50 cm`