Question

In the case of Huygens eyepiece, the ratio of focal length of eye lens, effective focal length and length of the eyepiece is :

• A. 1 : 2 : 3
• B. 2 : 3 : 4
• C. 2 : 1 : 3
• D. 3 : 2 : 4

Answer 1

The correct option is B 2 : 3 : 4

For Huygens eyepiece:

Focal length of eye lens = $f$

Effective focal length = $\frac{3f}{2}$

Length of eye piece = $2f$

So ratio of focal length of eye lens, effective focal length and length of the eyepiece is $=f$ : $\frac{3f}{2}$: $2f=2:3:4$

Answer. B) 2:3:4