# Help with radius of curvature and refractive index of lens

1. Mar 23, 2015

### jack hunter

Hi, I am a first time poster and I am completely lost with this question. Any help would be greatly appreciated

Filling the space between a contact lens and the cornea is a small quantity of liquid of refractive index of 1.336. Assuming the refractive index of the lens material is 1.490 find the effect on the power of the system of changing the radius of curvature of the posterior surface of the contact lens from 8 mm to 7 mm.

2. Mar 23, 2015

### BvU

Hello Jack, welcome to PF !

In the PF world it's a good custom posters adhere to the template. It's really beneficial for all, so its use has been made mandatory (see guidelines) .

Same thing for an attempt at solution. It helps to provide adequate assistance instead of rehashing things the poster already knows, or (worse) robbing him/her of the learning experience.

So tell us what you have been made familiar with in the lectures or in your preceding studies, find some equations that apply and show what you've found, tried and/or rejected so far. We'll help you further if we can.

Oh, and there's no need to post the same thing twice in different fora. There are good spirits floating around that start becoming nasty when they bump into such a thing.

3. Mar 23, 2015

### jack hunter

ok, so what I know so far:

The equation I am supposed to use I think is F= (n-1)((1/r1) - (1/r2)). Thats all I know.

4. Mar 23, 2015

### BvU

Seems like a good idea. How did you get it ?

If you know how to apply it, there's nothing holding you back. Perhaps you can post wat you find.

If you don't know what the equation is about, or how to apply it with multiple n (may not even be necessary), now is the time to go and find out. From your notes, the book, or the web .

5. Mar 23, 2015

### jack hunter

Im doing a unit were I have to do extra studies which are not really touched on in the lecture notes. So, I quite out of my ball park on this one, and Im completely lost of the two different n values.

6. Mar 23, 2015

### BvU

Well, play around a bit with this lens maker formula (also here ?). Make a drawing, show some work so that potential helpers can come into action (see post #2)