In an astronomical telescope in normal adjustment a straight black line of length `L` is drawn on inside part of objective lens. The eye piece forms a real image of this line. The length of this image is `I`. The magnification of the telescope is

Options

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

Answer

C

Explanation

Magnification by eyepiece
`m = (f)/(f + u)`
`- (l)/(L) = (f_(e))/(f_(e) + [- (f_(o) + f_(e) )] ) rArr (l)/(L) = (f_(e))/(f_(o))`
`m = (f_(o))/(f_(e)) = (L)/(l)`.