Physics Help Forum Magnifying glass

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 May 26th 2008, 06:21 PM #1 Senior Member   Join Date: Apr 2008 Location: HK Posts: 886 Magnifying glass When a magnifying glass is moved closer and closer to my eyes, the magnified image seen through lens becomes smaller and at a certain distance it becomes blurred. Why would it become blurred? Is it because of the minimum distance that can be seen by eye or of other reason? By constructing a ray diagram, it seems that there would not be blurred. Has I construct the ray diagram in a wrong way?
May 27th 2008, 04:37 AM   #2

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 Originally Posted by werehk When a magnifying glass is moved closer and closer to my eyes, the magnified image seen through lens becomes smaller and at a certain distance it becomes blurred. Why would it become blurred? Is it because of the minimum distance that can be seen by eye or of other reason? By constructing a ray diagram, it seems that there would not be blurred. Has I construct the ray diagram in a wrong way?
Note that when you look through a telescope or microscope that the image is blurry unless you have the lenses set just right. The reason the images are blurry except for at that one setting is because the image only forms in one place. Now consider that when someone else looks in the same telescope or microscope that they need to refocus the device. Why? Because there is another lens involved: the one in your eye.

The lens in your eye is an "autofocussing" device: the lens changes shape so we can see at different distances. So in your question when you move the lens closer and closer to your eye the image distance changes making your eye refocus. Is there a point to where your eye cannot correctly adjust to see the image properly? Of course.

-Dan
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Dec 14th 2008, 08:17 AM   #3
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 Originally Posted by werehk When a magnifying glass is moved closer and closer to my eyes, the magnified image seen through lens becomes smaller and at a certain distance it becomes blurred. Why would it become blurred? Is it because of the minimum distance that can be seen by eye or of other reason? By constructing a ray diagram, it seems that there would not be blurred. Has I construct the ray diagram in a wrong way?
Because we our eye lens has a point beyond which image formed is not clear, we have to strain to see it, normally it is 25 cm from eye, go nearer to eye and it will start to blur..

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