A man is looking at a small object placed at his near point. Without altering the position of his eye or the object, he puts a simple microscope of magnifying power $5\times$ before his eyes. The angular magnification achieved is

When we see an object, the image formed on the retina is

In which of the following the final image is erect?

Mark the correct options.

The focal length of the objective of a compound microscope is $f_o$ and its distance from the eyepiece is $L$. The object is placed at a distance $u$ from the objective. For proper working of the instrument,

A simple microscope has a magnifying power of $3.0$ when the image is formed at the near point ($25 \mathrm{cm}$) of a normal eye.

(a) What is its focal length?

(b) What will be its magnifying power if the image is formed at infinity?