- #1

- 1

- 0

You are using an out of date browser. It may not display this or other websites correctly.

You should upgrade or use an alternative browser.

You should upgrade or use an alternative browser.

- Thread starter jias
- Start date

- #1

- 1

- 0

- #2

- 103

- 0

Assume the convex lens creates an image of S at the point S'. Now if you put a concave lens in front of the convex one then the image of S will move further and will be at point S''. Now consider a reverse path of light: S'' is now the object and you'll see it's image at S' which is created by the concave lens. Let the distance from the "center" of the concave lens to S'' be a and the distance from S' to the "center" of the concave lens be b. Then using the lens formula:

[tex] -\frac{1}{f}=\frac{1}{a}-\frac{1}{b} [/tex] notice there is a minus near b and f. It's because the image is imaginary

Thus

[tex] f=\frac{ab}{b-a} [/tex]

I hope I didn't make any mistakes

- #3

tiny-tim

Science Advisor

Homework Helper

- 25,836

- 254

If you'd changed "Then using the lens formula:" to "Then use the lens formula! ",

(The OP can always come back and ask for more help, if necessary, of course )

- #4

- 103

- 0

Share:

- Replies
- 4

- Views
- 6K