Multiple Lens System(Objectless and Parallel Rays)

[JohnGaltis]

Homework Statement

Consider a telescope composed of two convex lenses, the objective lens and the eyepiece. The objective lens has a focal length of 26cm. Rays parallel to the principle axis enter the telescope through the objective lens and exit the telescope from the eyepiece as parallel rays. If the distance between the two lens is 30cm, find the focal length of the eyepiece.

Homework Equations

1/f = 1/d(object) +1/d(image)

The Attempt at a Solution

I am used to solving questions where rays come from an object and plugging in values. When rays are parallel and doesn't converge, how do I solve such a question? How do I start?

I know the rays entering the objective lens will converge on the focal point(26cm) since they are parallel rays.

Is the focal length of the eyepiece 4cm? (30cm-26cm)

 

[BvU]

Hello John,

According to your relevant equation: yes.
Make a drawing to check this out !

 

[JohnGaltis]

Ah- thank you, ByU.