# We will use huygens principle 1678 all points on a

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Unformatted text preview: )min = (d/m)Δ(sinθ)min = λ/mN: Δλmin λ sinθ λ 1 = Nm Nd Comments: • It pays to use a grating that has a large number of lines, N. However, one must illuminate them all to get this benefit. • It also pays to work at higher order (larger m): The widths of the peaks don’t depend on m, but they are farther apart at large m. First order m=1 0 Second order m=2 Third order m=3 λ/d 2λ/d 3λ/d sin θ Lecture 4, p 19 Huygens’ principle A Consequence of Superposition We will next study what happens when waves pass through one slit. We will use Huygens’ principle (1678): All points on a wave front (e.g., crest or trough) can be treated as point sources of secondary waves with speed, frequency, and phase equal to the initial wave. Wavefront at later time Wavefront at t=0 Q: What happens when a plane wave meets a small aperture? A: The result depends on the ratio of the wavelength λ to the size of the aperture, a: λ << a λ >> a The transmitted wave is concentrated in the forward...
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## This note was uploaded on 03/27/2014 for the course PHYS 214 taught by Professor Staff during the Spring '08 term at University of Illinois, Urbana Champaign.

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