lecture36 - Limits on Resolution (38.3) - diffraction...

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- diffraction through a circular hole - angular resolution of telescopes - resolution of microscopes Limits on Resolution Limits on Resolution (38.3) Practice: Chapter 38, problems 17, 19, 21. 1) Narrow slit: θ 1 slit Intensity θ 1 = λ / a “angular width” of central peak is 2 ( λ / a ) (radians). Diffraction Diffraction
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Diffraction through a circular aperture: Intensity Diameter D Image on Screen The angle θ 1 from the centre to first dark ring (“angular radius” of central spot) is about 1.22 λ /D radians. θ 1 1.22 λ /D Image (perfect focus) Stars (point sources at infinity) A “perfect” telescope only magnifies the diffraction pattern of the circular “hole” it looks through. a n g le 1 .2 λ /D Resolution of a Telescope Resolution of a Telescope * * D telescope lens
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Rayleigh Criterion Criterion Not Resolved Images are just resolved when the centre of one pattern overlaps the first dark line of the other pattern. Rayleigh
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lecture36 - Limits on Resolution (38.3) - diffraction...

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