34. Wave Optics

A diffraction grating with $500\text{lines}/\mathrm{mm}$ is illuminated by two wavelengths of light: $450\mathrm{nm}$ and $600\mathrm{nm}.$ What is the distance between the $m=2$ bright fringes of the two colors of light on a screen $1.3\mathrm{m}$ away?

A diffraction grating has$500\text{lines}/\mathrm{mm}.$ If it is illuminated by a laser at$532\mathrm{nm},$ how many bright spots will be observed on a screen placed behind the grating?

A particular kind of oil with an index of refraction of $1.46$ has spilled on water. The different thicknesses of the oil slick result in different colors being strongly reflected at different parts of the spill. But near the edges, you identify the thinnest part of the oil layer that strongly reflects green light with a wavelength of 550 nm when you are directly overhead. What is the thickness of the oil at this point? Assume light is incident normal to the oil surface.