In a vacuum, the wavelength is 589 nm. Light passes through a thin layer with refractive index n=1.93 and thickness is 0.76 mm. How many wavelength fit into the layer?

Suppose that f : rn → rm and that a ∈ k, where k is a connected subset of rn . suppose further that for each x ∈ k there exists a δx > 0 such that f(x) = f(y) for all y ∈ bδx (x). prove that f is constant on k; that is, f(x) = f(a) for all x ∈ k