<A NAME="top"></A> Physics Review Question

Unit: Year: 1992 Question#: 89
Question: If the distance between an object and a concave (converging) mirror is more than twice the focal length of the mirror, the image formed will be
(1 ) real and behind the mirror
(2 ) real and in front of the mirror
(3 ) virtual and behind the mirror
(4 ) virtual and in front of the mirror

What is this question really asking?




Explanation by: Apia A

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<A NAME="answerA"></A>
Answer 1
real and behind the mirror

INCORRECT

This answer can not be correct because for a mirror an image cannot be real and behind the mirror. If an image in a mirror is real it is on the same side as the object .





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<A NAME="answerB"></A>
Answer 2
real and in front of the mirror

CORRECT

For concave mirrors an image is real if the object distance is greater than the focal length and so in this question the object length is twice the focal length. This means that the image is real and since the image is real it must be both real and in front of the mirror.







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<A NAME="answerC"></A>
Answer 3
virtual and behind the mirror

INCORRECT

Since the object is outside the focus the image cannot be virtual.



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<A NAME="answerD"></A>
Answer 4
virtual and in front of the mirror

INCORRECT

(The same as 3) The image cannot be virtual

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<A NAME="what"></A>
What's this question really asking?
When is the image in a concave (converging ) mirror real or virtual?




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