Yes, I don't see a way to connect the 6250 angstroms and the fact that each wavelength must be a multiple of a half. There must be some equation I'm missing, but I just can't figure out the problem.
I apologize for not clarifying wavelength, but I intended to. As for the film, I believe it means some form of glass, but its not really relevant to the solution of my problem.
Homework Statement
If the apparatus for showing Newton's rings is illuminated with light at 6250 A (angstroms), what thickness of film underlies each of the first three light rings?
Homework Equations
2D (the thickness of the film) equals a multiple of 1/2 of a wavelength
1 angstrom =...