How do you determine the image size formed by a convex lens?

[kriegera]

Homework Statement

A candle is placed 10 inches from a convex lens whose focal length is 5 in. Where will the image be formed? How large an image is formed?

Homework Equations

The Attempt at a Solution

Here we use the following formula to find where the image will be formed:
1/f=1/Do+1/Di  1/Di=1/f-1/Do =
1/Di=1/5-1/10 = 2-1/10 = 10 in.


Here's the equation to solve part B but I don't know how to figure "So" which would be dimensions of the candle. Any help?

Si=So(Di/Do) =
Si=So(10/10) =

 

[AtticusFinch]

Well you can't give a numerical answer but you can say that the image formed is the same height as the object.

 

[kriegera]

Well you can't give a numerical answer but you can say that the image formed is the same height as the object.

So, there's no numerical way to solve without being given the height of the object?

 

[AtticusFinch]

So, there's no numerical way to solve without being given the height of the object?

Nope, because that would mean that the image height does not depend on the object height which is clearly not true.