Wave Optics

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Each point on a wavefront acts as a source of secondary wavelets. The new wavefront at any later time is the forward envelope of these secondary wavelets. For example, when light passes through a narr…

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The direction of propagation of a wave is perpendicular to the wavefront. For example, in a plane wave, the wavefronts are flat planes, and the light travels perpendicularly to these planes.

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Constructive interference occurs when the path difference between waves from the two slits is an integral multiple of the wavelength (nλ). This means the waves arrive in phase, crest to crest, resulti…

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Coherent sources emit light waves of the same frequency and constant phase difference. Our eyes cannot act as coherent sources because they do not emit light; they only receive it.

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Using μ = λ_air / λ_medium: - For 384 nm: μ₁ = 600 / 384 = 1.56 - For 589 nm: μ₂ = 600 / 589 ≈ 1.02 - For 760 nm: μ₃ = 600 / 760 ≈ 0.79 Answer: 1.56, 1.02, 0.79…

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Fringe width (β) is the distance between two consecutive bright or dark fringes. Formula: β = λD / d Where λ = wavelength, D = slit-to-screen distance, d = slit separation. Example: If λ = 600 nm, D =…

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When one slit is closed, interference stops and diffraction occurs. Instead of alternate bright and dark fringes, we get a broad central maximum with dimmer secondary maxima on either side due to sing…

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Given: d = 2 mm = 0.002 m, D = 100 cm = 1 m, x = 5 cm = 0.05 m Path difference Δ = (d/D)x = (0.002 / 1) × 0.05 = 0.0001 m = 0.1 mm Answer: 0.1 mm…