Q. A needle is placed away from a convex mirror of focal length . Give the location of the image and the magnification. What happens as the needle is moved farther from the mirror?

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Solution:

image
Given, focal length of convex mirror
(Focal length of convex mirror is taken as positive)
Distance of object
Size of object
Using the mirror formula,




Distance of image from the mirror T
he positive sign shows that the image is formed behind the mirror.
Using the formula of magnification,


Size of image
As is positive, so image is erect and virtual.
Magnification is given by

As the needle moves away from the mirror, the image also moves away from the mirror (as and the size of image goes on decreasing.