Problem 5.85

Light with wavelength \(\lambda=0.55 \mu \mathrm{m}\) from a distant point source falls normally on the surface of a glass wedge. A fringe pattern whose neighbouring maxima on the surface of the wedge are separated by a distance \(\Delta x=0.21 \mathrm{~mm}\) is observed in reflected light. Find: (a) the angle between the wedge faces; (b) the degree of light monochromatism \((\Delta \lambda / \lambda)\) if the fringes disappear at a distance \(l \simeq 1.5 \mathrm{~cm}\) from the wedge's edge.