Question

In Ramsden's eyepiece, the focal length of each lens is $F$' . The distance of the image formed by the objective lens from the eye lens is:

• A. $\frac{14F}{15}$
• B. $\frac{13F}{14}$
• C. $\frac{12F}{13}$
• D. $\frac{11F}{12}$

Answer 1

The correct option is D $\frac{11F}{12}$

Distance between objective lens and eye lens is $\frac{2F}{3}$

Image formed by the objective lens is at $u=-\frac{-F}{4}$

So, distance of image formed by the objective lens from eye lens $=\frac{F}{4}+\frac{2F}{3}$$=\frac{3F+8F}{12}$ $=\frac{11F}{12}$