6.1Diffraction - Diffraction and Interference 6.1...

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1 6.1 Diffraction Diffraction grating Single slit diffraction Circular diffraction Diffraction and Interference • Diffraction and interference are similar phenomena. • Interference is the effect of superposition of 2 coherent waves. • Diffraction is the superposition of many coherent waves. Diffraction grating • Consists of a flat barrier which contains many parallel slits separated by a short distance d. • A parallel monochromatic light beam passing through the grating is diffracted by an angle θ similar to two slit interference. However, the intensity of the diffracted light is higher and the peaks are much narrower. dsin θ =m λ Diffraction grating two slit interference d multi-slit interference Diffraction grating dsin θ =m λ m=0 m=1 m=2 m=-1 m=-2 m=0 m=1 m=2 m=-1 m=-2 λ Higher intensity Question A grating in a spectrometer has a length of 2 cm and has contains 10 4 lines. Find the first order diffraction angle for light with a wavelength of 500 nm. first order m=1 dsin θ =m λ 9 6 m5 0 0 x 1 0 sin 0.25 d2 x 1 0 λ θ= = = θ =14.5 o θ 2 6 4 2x10 m 2x10 m 10 == L=2.0 cm N =10 4 slits L d N = Use of a diffraction grating in a spectrometer Dispersion of light of different wavelengths
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2 Optical compact disc 10 -6 m The closely spaced dots act like a diffraction grating. Single slit diffraction barrier a λ For single slit diffraction the complex behavior of the wave as a function of the aperture a is explained by interference between multiple coherent point sources in the slit.
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This note was uploaded on 06/03/2010 for the course PHYS physics 1c taught by Professor Smith during the Spring '09 term at UCSD.

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6.1Diffraction - Diffraction and Interference 6.1...

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