Magnifying power of a simple microscope is (when final image is formed, at D=25cm from eye)

Options

A. `(D)/(f)`
B. `1 + (D)/(f)`
C. `1 + (f)/(D)`
D. `1 -(D)/(f)`

Answer

B

Explanation

When final image is formed at D = 25 cm from eye. In this situation, `v=-D` from lens formula,
`(1)/(v)-(1)/(u)=(1)/(f)`,
we have, `(1)/(-D)-(1)/(-u)=(1)/(f)`
i.e., `(D)/(u)=1+(D)/(f)`
So, Magnifying power `=(D)/(u)=(1+(D)/(f))`