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3 Cards in this Set
- Front
- Back
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Diffraction |
- wave phenomenon of light - ability of light to bend around edges of an obstruction or through a narrow opening - all waves are subject to diffraction when they encounter obstruction/aperature/irregularity in medium - creates a secondary wave front - out of phase with the primary wave - interference with the primary wave front - changes direction of the wave - corresponds to bending of light ray - shorter the wavelength (e.g. blue light) = reduced diffraction - smaller aperture = increased diffraction |
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Airy Disc |
- when light passes through a circular aperture - circular diffraction pattern produced. - central disc surrounded by alternating dark and light rings - image formed on the retina from a distant source takes form of concentric light and dark rings surrounding a bright central disc - Diameter (d) = 2.44f (focal length) / diameter of pupil - longer wavelength - large diameter of Airy disc - optical system free of aberration will form an airy disc on image plane. |
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Limits of resolution - resolving power |
- smallest angle of separation between 2 points - allows formation of 2 discernible images by the optical system. - reached when 2 Airy discs separated such that the centre of 1 falls on the dark ring of the other. |
