PHYSICS 7E Lecture Notes - Lecture 28: Airy Disk, Diffraction, Hubble Space Telescope
PHYSICS 7E - Lecture 28 - Diffraction
*Images from University Physics, Young & Freedman
Circular Apertures
●An aperture of any
shape forms a diffraction pattern
●Figures below illustrate diffraction by a circular aperture. The airy disk
is the central
bright spot
●The first dark ring occurs at an angle given by inθ .22 λ/Ds 1= 1
Diffraction and Image Formation
●Diffraction limits the resolution of optical equipment, such as telescopes
●The larger the aperture, the better the resolution. Figures below illustrates this effect
(a) Small aperture
(b) Medium aperture
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Document Summary
An aperture of any shape forms a diffraction pattern. Figures below illustrate diffraction by a circular aperture. The first dark ring occurs at an angle given by in bright spot s. Diffraction limits the resolution of optical equipment, such as telescopes. The larger the aperture, the better the resolution. Figures below illustrates this effect (a) small aperture (b) medium aperture (c) large aperture. For a circular aperture of diameter d. Resolution is the distance at which a lens can barely distinguish two separate objects. Resolution is limited by aberrations and by diffraction. Aberrations can be minimized, but diffraction is unavoidable; it is due to the size of the lens compared to the wavelength of the light. The rayleigh criterion states that two images are just resolvable when the center of one peak is over the first minimum of the other. Because of diffraction, large-diameter telescopes, such as the vla radio telescope below, give sharper images than small ones.
