# hw27 - Physics 21 Fall, 2004 Solution to HW-27 36 P 54 When...

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Physics 21 Fall, 2004 Solution to HW-27 36 P21 The normal lens of a 35 mm camera has a fo- cal length of 50 mm. Its aperture diameter varies from a maximum of 25 mm ( f/ 2) to a minimum of 3.0 mm ( 16). Determine the resolution limit set by diFraction for 2and 16. Specify as the number of lines per millimeter resolved on the ±lm. Take λ = 500 nm. ²or a lens diameter a , the angular distance from the cen- ter of the diFraction pattern of a line to the ±rst zero will be 1 . 22 λ/a . Assuming the lens is focussed at in±nity, the distance to the ±lm will be the focal length f , so the actual distance will be 1 . 22 fλ/a . This distance is the closest spac- ing of two just-resolved lines. The number of lines per unit length N resolvable on the ±lm will be the reciprocal of this distance, N = a 1 . 22 . ²or f =50mmand λ = 500 nm, a =25mm 820 / mm ,a =3mm 98 / mm . 36 P34 Missing orders occur for a diFraction grating when a diFraction minimum coincides with an interference maxi- mum. Let a be the width of each slit and d the separation of
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## This note was uploaded on 08/06/2008 for the course PHYS 21 taught by Professor Hickman during the Fall '07 term at Lehigh University .

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