Radius of curvature of second lens surface

[desmond iking]

Homework Statement

A lens of power of -5.0D has a surface which is convex of radius of curvature of 15.0cm. The lens is made of material of refractive index of 1.50.
What's the radius of the other surface of lens?

Homework Equations

The Attempt at a Solution

since power = 1/f
so i have (1/ (-1/5) )= ( (1.5-1)/ 1) x ( (1/15) + (1/r2) )
i found out my r2 = -0.10cm.
But the correct ans given is -6.0cm.

 

[Hardik Batra]

Here, lens of power = -5.0D. (1 Diopter = 1m^-1)

And you have taken the P = 1/f, here f is in "meter", but you have taken R1 = 15 cm which is in "cm."

Don't you think this is weird.