If the focal length of the objective lens is increased then

Options

A. Microscope will increase but that of telescope decrease
B. Microscope and telescope both will increase
C. Microscope and telescope both will decrease
D. Microscope will decrease but that of telescope will increase.

Answer

D

Explanation

The magnifying power of the microscope (for normal adjustment) is given by :
`m=(L)/(f_(o))xx(D)/(f_(e))`
`rArr" "m prop (1)/(f_(o))`
The magnifying power of the astronomical telescope (for normal adjustment) is given by :
`m=(f_(o))/(f_(e))`
`rArr" "mprop f_(o)`
If the focal length of the objective lens is increased, then the magnifying power of microscope will decrease but that of the telescope will increase.