In a simple microscope, if the final image is located at infinity then its magnifying power is
A
$$\displaystyle\frac{25}{f}$$
B
$$\displaystyle\frac{D}{25}$$
C
$$\displaystyle\frac{f}{25}$$
Correct option is A. $$\displaystyle\frac{25}{f}$$
Given, in a simple microscope, the final image is formed at the infinity.
We know, least distancefor distinct vision in simple microscope is $$D=25cm$$.
Again we know, when the final image in a simple microscope is formed at infinity, the object must be situated at the focus $$f$$.
$$\therefore$$ When the image is at infinity, magnifying power of the microscope is
$$m=\dfrac{D}{f}=\dfrac{25}{f}$$
So, the correct option is (A).