Focus of Lens Submerged In Water

[JSGandora]

Homework Statement

A glass lens (n=1.50) in air has a power of +5.2 diopters. What would its power be if it were submerged in water?

Homework Equations

Not too sure. May be Lensmaker's Equation, Snell's Law, and Power of a Lens Equation.

The Attempt at a Solution

I'm trying to derive the Lensmaker's Equation with the surrounding substance having index of refraction 1.33 but that didn't work. I also tried changing the index of refraction of the lens so that it was with respect to the speed of light in water rather than in air.

 

[tiny-tim]

Hi JSGandora!

Try the thin https://www.physicsforums.com/library.php?do=view_item&itemid=148" equation …

show us what you get ​

 

[JSGandora]

Haha, I found it.

I have found the solution to be 1.3 diopters. You just divide the refractive index of the lens by that of the water to get the effective refractive index from Snell's Law. That derivation of the Lensmaker's equation holds true so we get $\left(\frac{1.5}{1.33}-1\right)(10.4)\approx \boxed{1.3D}$. I got the same concept last night without knowing that it was correct because I didn't subtract 1 from the ratio of refractive indices. >.<