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Old Dec 17th 2008, 06:15 PM   #1
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Unsolvable Question? Regarding Mirrors

I got this question on a test and I think it is a completely unfair question... to me the way it is worded there is no way to positively determine an answer with the given information.

Q) a) What type of mirror would you use to produce an upright image with magnification of 7.5 when an object is located 14.0 mm from a door? The correct answer was Concave which is what I put but the secon part of the question is impossible to solve with the given information IMO.


b) The radius of curvature is:?



*note no graph paper was provided

Last edited by BC_STS; Dec 17th 2008 at 06:23 PM.
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Old Dec 18th 2008, 07:23 PM   #2
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Originally Posted by BC_STS View Post
I got this question on a test and I think it is a completely unfair question... to me the way it is worded there is no way to positively determine an answer with the given information.

Q) a) What type of mirror would you use to produce an upright image with magnification of 7.5 when an object is located 14.0 mm from a door? The correct answer was Concave which is what I put but the secon part of the question is impossible to solve with the given information IMO.


b) The radius of curvature is:?



*note no graph paper was provided
Note that radius of curvature = 2 x focal length , focal length,which can be found by mirror formula
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Old Dec 18th 2008, 11:16 PM   #3
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The formulas we use are :

like you said C = 2f

and

1/f = 1/do + 1/di

f = focal distance

do = distance object from mirror

di = distance of image from mirror

and

hi/ho = - di/do

and M = hi/ho or -di/do

M = magnification

hi = height of image

ho = height of object


in this quesition we are only given the magnification, we do not know where the mirror is in relation to the object nor do we know its size.

Last edited by BC_STS; Dec 18th 2008 at 11:19 PM.
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