Question

Define the magnifying power of a compound microscope when the final image is formed at infinity. Why must both the objective and the eyepiece of a compound microscope have short focal lengths? Explain.

Answer 1

Magnifying power is defined as the angle subtends at the eye by the image to the angle subtended by the object.

$m=m_0\times m_e=\frac{L}{f_0}\times \frac{D}{f_e}$

To increase the magnifying power both objective and eye piece must have short focal lengths such as,

$m=\frac{L}{f_0}\times \frac{D}{f_e}$