Question

A small postage stamp is placed in front of a concave mirror (radius = 1.4 m), such that the image distance equals the object distance. (a) What is the object distance? (b) What is the magnification of the mirror (with the proper sign)?

Answer 1

well your object distance would be at 2xs the focal point. but im not sure how your teacher asks you to find the focal point. you might have to measure it. and the magnification would be found by this formula:
image height / object height.

you find these by measuring and your focal point would be negative and your magnification will not be negative.

Answer 2

(a) When the object is located at the center of curvature, the image will also be located at the center of curvature. In this case, the image will be inverted .

so ,obejct distance=radius of mirror= (1.4m )

(b) magnification will be -1 as image is of equal size and inverted..

M= -1

Answer 3

Formula for concave mirror
1/v+1/u=2/R R=Radius of Curvature
in this case u=v so
u=v=R=1.4 m
Since the image and object at the same point the triangles are equal so magnification is one and the image is real.