# If the focal length of objective lens is increased then magnefying power of: Option 1) microscope will increase but that of telescope decrease. Option 2) microscope and telescope both will increase. Option 3) microscope and telescope both will decrease. Option 4) microscope will decrease but that of telescope increase.

S subam

Compound Microscope -

$m= -\frac{v_{o}}{u_{o}}\cdot \frac{D}{u_{e}}$

- wherein

$v_{o}\, and \, u_{o}$ is distance from objective.

$u_{e}$ Distance from eyepiece.

Maximum magnification $m= -\frac{v_{o}}{u_{0}}\left ( 1+\frac{D}{f_{e}} \right )$

Astronomical Telescope -

$m= \frac{-f_{o}}{f_{e}}\left ( 1+\frac{f_{e}}{D} \right )$

- wherein

$f_{o}$ = focal length of objective

$f_{e}=$ focal length of eyepiece

For microscope magnifying power $\propto \frac{1}{fo}$

For telescope magnifying power $\propto fo$

$\therefore$ magnifying power of microscope decreases and that of telescope increases

Option 1)

microscope will increase but that of telescope decrease.

This option is incorrect

Option 2)

microscope and telescope both will increase.

This option is incorrect

Option 3)

microscope and telescope both will decrease.

This option is incorrect

Option 4)

microscope will decrease but that of telescope increase.

This option is correct

Exams
Articles
Questions