If the focal length of the objective lens is increased then

Options

A. microscope will increases but that of telescope decrease.
B. microscope and telescope both will increase.
C. microscope and telescope both will decrease.
D. microscope will decreases but that of telescope will increase.

Answer

D

Explanation

Magnifying power of a microscope,
`m=((L)/(f_(0)))((D)/(f_(e)))`
where `f_(0)` and `f_(e)` are the focal lengths of the objective and eyepiece respectively and L is the distance between their focal points and D is the least distance of distinct vision.
If `f_(0)` increases, then m will decrease.
Magnifying power of a telescope, `m=(f_(0))/(f_(e))`
where `f_(0)` and `f_(e)` are the focal lengths of the objective and eyepiece repectively.
If `f_(0)` increases, then m will increase.