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 has short focal lengths? Explain.
Solution
Magnifying power is defined as the angle subtended at the eye by the image
to the angle subtended (at the unaided eye) by the object.
To increase the magnifying power both the objective and eyepiece must have short focal lengths such as 
