A lens for a 35-mm camera has a focal length given by f = 27 mm. How close to th
ID: 1508365 • Letter: A
Question
A lens for a 35-mm camera has a focal length given by f = 27 mm. How close to the film should the lens be placed to form a sharp image of an object that is 4.9 m away? What is the magnification of the image on the film? Consider a two-slit interference pattern, with monochromatic light of wavelength lambda. What is the path difference Delta l for the sixth bright fringe? Give your answer in terms of the wavelength of the light. What is the path difference Delta l for the ninth dark fringe above the central bright fringe? Give your answer in terms of the wavelength of the light. Does the path length difference Delta l increase or decrease as you move from one bright fringe of a two-slit experiment to the next bright fringe farther out? What is Delta l of the second bright fringe outside of the central bright fringe in terms of the wavelength lambda of the light?Explanation / Answer
9. Given: object distance do = 4.9 m; focal length f = 27 mm
Hence using lens equation: 1/di + 1/do = 1/f
di = 27*4900/(4900 - 27) = 27.15 mm
(a) So the distanc ebetween the film and the lens should be 27.15 mm for sharp image.
(b) Magnification m = -di/d0 = -27.15/4900 = -0.0055
10. Path difference for bright fringe is given by lbright = n and for dark fringe by ldark = (2n+1)*(/2)
(a) For sixth bright fringe l = 6*
(b) For ninth dark fringe l = 17/2* = 8.5*
11.
(a) From the above formula it's clear that path length increases for higher bright fringes.
(b) For second bright fringe l = 2*
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