Resolving power of telescope of aperture 100 cm for light of wave length 5500 a
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point object is imaged using a circular opening (or aperture) like a lens or the iris of our eye, the image formed is not a point but a diffraction pattern. This is true particularly when the size of the object is comparable to the wavelength of light.
Just as in single sight diffraction, a circular aperture produces a diffraction pattern of concentric rings that grow fainter as we move away from the center. These are known as Airy’s discs.
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Because of this point sources close to one another can overlap and produce a blurred image. The half angle θ subtended by the first minimum at the source is given by the relation
sinθ ≈ 1.22λ/d
To obtain a good image, point sources must be resolved i.e., the point sources must be imaged such that their images are sufficiently far apart that their diffraction patterns do not overlap. For this the minimum distance between images must be such that the central maximum of the first image lies on the first minimum of the second and vice versa
Just as in single sight diffraction, a circular aperture produces a diffraction pattern of concentric rings that grow fainter as we move away from the center. These are known as Airy’s discs.
0
Because of this point sources close to one another can overlap and produce a blurred image. The half angle θ subtended by the first minimum at the source is given by the relation
sinθ ≈ 1.22λ/d
To obtain a good image, point sources must be resolved i.e., the point sources must be imaged such that their images are sufficiently far apart that their diffraction patterns do not overlap. For this the minimum distance between images must be such that the central maximum of the first image lies on the first minimum of the second and vice versa
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