Question

Could anybody help pleaase. I don't understand thin-film interference!!
A thin film of gasoline on water, with a thickness of 364 nm, is illuminated by light of wavelength 510 nm. If the refractive index of gas is 1.40 and that of water is 1.33, will constructive or destructive inteference occur for light falling perpendicular to the surface?
I reread the section so many times but I still couldn't understand the concepts. Could anybody help? Thanks!

Answer 1

Have a look at this, and the step-by-step process:
http://physics.bu.edu/~duffy/py106/Diffraction.html