Wave Optics

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A wavefront is the locus of all points having the same phase at a given instant of time. For example, in water waves from a stone dropped in still water, the wavefront is circular. The direction of wa…

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Huygens' Principle states that each point on a wavefront acts as a secondary source of light emitting spherical wavelets in all directions with the speed of light in the medium. The new wavefront is t…

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When a plane wavefront AB is incident at angle i on a reflecting surface, point A reaches the surface at t=0 and B at time T. Using Huygens' principle, secondary wavelets from A have radius vT at time…

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For refraction at a plane boundary: sin i/sin r = v₁/v₂ = n₂/n₁, giving n₁ sin i = n₂ sin r (Snell's law). The wavelength changes in different media: λ₂ = λ₁(v₂/v₁) = λ₁(n₁/n₂). In a medium with refra…

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Polarization is the phenomenon of restricting the oscillations of the electric field of light to one particular direction perpendicular to the direction of propagation. Unpolarized light has electric …

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Malus' law states: I₂ = I₁ cos²θ, where I₁ is intensity of incident polarized light, I₂ is transmitted intensity, and θ is angle between polarization axes of polarizer and analyzer. When unpolarized l…

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Brewster's angle (θB) is the angle of incidence at which reflected light is completely plane polarized. At this angle, reflected and refracted rays are perpendicular. From geometry: θB + θr = 90°. Usi…

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Coherent sources are sources that emit waves of the same frequency with a constant phase difference (independent of time). They are essential for sustained interference patterns because: 1) Same frequ…