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Interference of Light

Problem 5.85

Light with wavelength λ=0.55μm\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 Δx=0.21 mm\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 (Δλ/λ)(\Delta \lambda / \lambda) if the fringes disappear at a distance l≃1.5 cml \simeq 1.5 \mathrm{~cm} from the wedge's edge.

Reveal Answer
 (a) Θ=1/2λ/nΔx=3′; (b) Δλ/λ≈Δx/l=0.014 . \text { (a) } \Theta=1 / 2 \lambda / n \Delta x=3^{\prime} ; \text { (b) } \Delta \lambda / \lambda \approx \Delta x / l=0.014 \text { . }
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