(20%) (a) (4%) Explain the coherence of wave and state its importance for interference. (b) (4 %) How to improve the interference result if you use a white-light bulb as the light source in Young's double slit experiment? (c) (4%) Explain why the degree of coherence of a laser is better than a light bulb. (d) (4%) A thin film of ZnS (n=2.37) is used to coat a camera lens (ng-1.53) so that it is antireflecting at a wavelength of 550 nm under normal incidence. Find the minimum thickness of the thin film. (e) (4%) A thin film of MgF2 (n= 1.38) is used to coat a camera lens (ng-1.53) so that it is antireflecting at a wavelength of 580 nm under normal incidence. What wavelength is minimally reflected when the light is incident instead at 45⁰?
