3) A Fabry-Perot interferometer with fixed plate spacing t = 1.50mm is used to examine filtered light from a helium lamp, with wavelength lambda = 587.56nm. The plates have reflectance R = 0.950.
a) What is the free spectral range (in nm) for this spacing t and wavelength lambda?
b) What is the smallest resolvable wavelength difference for this setup?