Unit: optics
Year: 1990 Question#: 100
Question: A student places her eyeglasses directly on a printed page. As she raises them, the lenses cause the image of the print to remain erect while gradually decreasing in size. She should conclude from this that the lenses of the eyeglasses are:
(1 ) polarized
(2 ) plane
(3 ) converging
(4 ) diverging
What is this question really asking?
Explanation by: Kevin E
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Answer 1
polarized
INCORRECT
Polarized lenses only let light that is angled (polarized) in a certain direction, but it doesn't bend the light to alter the image in any way. The only effect a polarized lens would have would be to darken the image somewhat.
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Answer 2
plane
INCORRECT
A plane lens has no curvature, so it won't alter the image at all. Although the light will bend as it enters the lens, it will bend the same amount as it exits the lens.
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converging
INCORRECT
As a converging lens pulls away from an object that is within its focal length, the image size increases.
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diverging
CORRECT
As the diagram below shows, as you move the lens away from the object, the image does get smaller, which is what's described.
return to top What's this question really asking?
You must find what type of lens will give you an erect image that decreases in size as the object distance increases. return to top
