Question

In the case of Ramsden's eyepiece, if the distance of cross wires from the field lens is 1.2 cm, the distance of cross wires from the eye lens is :

• A. 3.3cm
• B. 3.6 cm
• C. 4.4 cm
• D. 4.8 cm

Answer 1

Answer: (C)

4.4 cm

Distance of cross wire from field lens $=f/4=1.2cm$

$\Rightarrow f=4.8cm$

Distance of cross wire from eye lens $=\frac{f}{4}+\frac{2f}{3}$ = $\frac{11f}{12}=4.4cm$