Unit: Geometric optics
Year: 1995 Question#: 87
Question: A concave mirror has a radius of curvature of 0.60 meter. When an object is placed 0.40 meter from the reflecting surface, the image distance will be
(1 ) 0.10 m
(2 ) 0.20 m
(3 ) 0.83 m
(4 ) 1.2 m
What is this question really asking?
Explanation by: Chris
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Answer 1
0.10 m
INCORRECT
This would be the answer if you you subtracted the object distance from .3, the focal radius. Remember to use the equation 1/di+1/do=1/F. Using the reciprocals of the numbers above will yield the right answer. return to top
Answer 2
0.20 m
INCORRECT
Subtracting the object distance from the radius of curvature is not the way to find the right answer. return to top
Answer 3
0.83
INCORRECT
.83 is incorrect
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Answer 4
1.2 m
CORRECT
Radius of curvature=2f
Focal length=f
Focal length=Radius of curvature/2
f=.6/s
f=.3m
solve for the image distance
return to top What's this question really asking?
This question is asking how far an image of an object will appear from the mirror in a concave mirror. return to top
