If the focal length of objective lens is increased, the magnifying power of

Microscope will decrease & telescope will increase

The correct answer is Option (2) → Microscope will decrease & telescope will increase

For microscope,

Magnifying power = $\frac{L D}{f_0 f_e}$

Hence, $M P \propto \frac{1}{f_0}$

For telescope

Magnifying power $=\frac{f_{\circ}}{f_e}$

Hence, $M P \propto f_0$