- #1

- 212

- 0

## Homework Statement

A converging lens of focal length f forms a real image of an object. Show that the smallest separation of the object and the image is 4f.

## Homework Equations

I think:

[tex]\frac{n_1}{s_0} + \frac{n_2}{s_1} = \frac{n_2 - n_1}{R}[/tex]

small angle approximations.

## The Attempt at a Solution

I've not gotten too far with this.

As I understand it (I missed a couple of lectures at the end of last week and the start of this week due to illness, and am working from un-annotated handouts), s1 = f?

So in that case I assume that I need to rearrange the equation above to give me s0 in terms of f (which I would assume to be 3f as the total separation is s0 + s1).

I've tried taking this approach, and I can't seem to get rid of R or the n's within the equation, and I'm not sure what substitutions to make (they dont seem obvious from the diagrams - I would assume that they'd be trigonometrical ones).

Any help with this would be greatly appreciated.