Question

A convex lens of a focal length 5 cm is used as a simple microscope. Where should an object be placed so that the image formed by it lies at the least distance of distinct vision (D = 25 cm)?

Answer 1

f = 5 cm

v = - 25 cm

We know that, `1/"v" - 1/"u" = 1/"f"`

`=> -1/25 - 1/"u" = 1/5`

`=> -1/"u" = 1/25 + 1/5`

`=> 1/"u" = -((1+5)/25) = - 6/25`

`therefore "u" = - 25/6 "cm" = - 4.16` cm