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posted by  eo on 11/12/2007 5:24:46 PM  |  status: Live  |  Earned Karma: 53

thin lens

Course Textbook Chapter Problem Needs by
Algebra Based Physics Physics: Principles with Applications (6th) by Giancoli 23 49P N/A
Question Details:
A 84mm focal-length lens is used to focus an image on the film of a camera.  The maximum distance allowed between the lens and the film plane is 120 mm.  How far ahead of the film should the lens be if the object to be photographed is at the following distance from the lens?
a) 13.4 m away
b) 3.5 m away
c) 0.9 m away
d) what is the closest object this lens could photograph sharply?
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posted by Astle on 11/12/2007 10:44:34 PM  |  status: Live
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Response Details:
 
from the lense formula
              1/f = 1/u +1/v
 f - focal length of the convex lense
 v - distance of the image
 u - distance of the object .
 
              given f = 0.084 m
                       v = 0.012 m
                 from the above equaiton we can solve for the  the value of 'u'.
 
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posted by Anonymous on 4/6/2009 9:44:16 PM  |  status: Live
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A 84mm focal-length lens is used to focus an image on the film of a camera.  The maximum distance allowed between the lens and the film plane is 120 mm.  How far ahead of the film should the lens be if the object to be photographed is at the following distance from the lens?
a) 13.4 m away
b) 3.5 m away
c) 0.9 m away
d) what is the closest object this lens could photograph sharply?
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posted by Anonymous on 4/14/2009 2:57:47 PM  |  status: Live
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Using and given do & f we can find di.
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posted by Anonymous on 4/14/2009 3:12:54 PM  |  status: Live
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Response Details:
solution to d)

Use image distance, di, as the max distance between lens and film plane, 120mm.  Use the given focal length, 72mm.  Use the equation given 
.

Solve for do.
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posted by Anonymous on 11/6/2009 5:56:51 PM  |  status: Live
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The Lense is a converging lense (the kind of lense used in a camera) to produce an upright, real image.  The Focal length is given, and stays the same throughout the problem.  The object distance is usually what is given in the problem (the distance from the object to the lense).  The image distance is the distance from the lense to the film.  The focal distance is positive, since it is on the opposite side of the lense as the object.  The image distance is positive, since it is on the opposite side of the lense as the object.  And the object distance is also positive.  Just use the values in the lense equation

The final portion of the question (on mastering physics) asks for the closest an object can get while still remaining clear.  This is solved the same way, but different information is given.  The image distance is the farthest distance that the film can be from the lense, and this information is given in the text of the problem.  The object distance is what you must calculate.  The focal length remains the same.  All sign conventions are the same as in previous parts of this problem.
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