Curved glass and Newton's Rings

[semper_deere]

Homework Statement

A piece of curved glass has a radius of r=10m and is used to form Newton's Rings. Not counting the dark spot in the center of the pattern, there are one hundred dark fringes the last one on the outer edge of the curved piece of glass. The light being used has a wavelength of 654 nm in a vacuum. What is radius R of the outermost dark ring in the pattern?

Hint:r >> R you may assume Tan(theta)= theta for small angles, where theta must be expressed in radians.
lamda = 654 E-9 m= 100

Homework Equations

the only equation that I can find that is even close is Sin(theta)= m* lamda/ W that is use for single slit diffraction. I really do not know how to set this up. The hint is no help to me at all.

 

[Kurdt]

I believe the following page should aid you.

http://www.fas.harvard.edu/~scdiroff/lds/LightOptics/NewtonsRings/NewtonsRings.html