A parallel beam of light of wavelength 5890 A0 is incident on a glass plate having refractive index 𝝁=𝟏.𝟓 such that the angle of refraction in the plate is 600. Calculate the smallest thickness of the glass plate which will appear dark by reflected light.
A wedge shaped air film having angle 40 seconds is illuminated by monochromatic light. Fringes are observed vertically through a microscope. The distance between 10 consecutive dark fringes is 1.2 cm. find the wavelength of monochromatic light used.
Explain how interference in wedge shaped film is used to test optical flatness of given glass plate.