plane mirror

Discussion in 'MCAT Study Question Q&A' started by Oh_Gee, Sep 5, 2014.

1. Oh_Gee 5+ Year Member

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i thought that for plane mirrors, image distance=object distance. is that not correct?
this question is from Next Step tutor

A woman stands 1m in front of a plane mirror. What is the magnification and distance from the woman to her mirror-image?

1. 1/2 and 2m
2. 1 and 1m
3. 2 and 1m
4. 1 and 2m

Explanation

1. 1/2 and 2m, incorrect, Uses image distance of 2m rather than 1m and inverts the magnification equation.
2. 1 and 1m, incorrect, Does not sum object and image distance for distance between woman and image.
3. 2 and 1m, incorrect, Uses image distance of 2m in magnification equation and distance from woman to image also incorrect.
4. 1 and 2m, correct.

2. DrDreams Captain of the U.S.S. Enterprise Gold DonorVerified Account 7+ Year Member

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Yes because she stands 1 meter away from the mirror, thus she is 1 meter away from the actual mirror. However, her reflection is 1 mirror within the mirror, so it seems as if her reflection is actually 2 meters away from the woman herself.

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3. OP

Oh_Gee 5+ Year Member

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so the distance from object to plane mirror is

d(object) + d(image)?

also thanks for the quick reply. was not expecting that lol

4. mehc012 Big Damn Hero 5+ Year Member

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Image distance does equal object distance...but both of those are measurements TO the mirror.
What they are asking you is for the distance from the woman to the mirror (object distance) PLUS the distance from the mirror to the image (image distance). Since those are equal, you simply double it.

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5. DrDreams Captain of the U.S.S. Enterprise Gold DonorVerified Account 7+ Year Member

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Sorry, Ive no idea about the equation. But it sounds right. The image is always double the distance of the object towards the mirror. So I would say Dimage=2Dobject.

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6. mehc012 Big Damn Hero 5+ Year Member

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Haha, yes, exactly...I was about 30s late on that one, sorry!

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7. mehc012 Big Damn Hero 5+ Year Member

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Yeah, it's right. To get the apparent distance from the object to the image, you have to add object distance and image distance.

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