Question

the magnification product by a mirror is +1.what does it mean?

Answer 1

the magnitude of magnification produced by the mirror is 1 it shows that the ratio of the size of image to the size of object is 1 or it means both the size of the image and object is equal.
it also says that the distance from object from the mirror is equal to the distance of image behind the mirror.

Answer 2

"The magnification product by a mirror is +1. "The actual meaning of this sentence is that the the image formed by the plane mirror is same or equal to the  size as that of the object.
 
 Since we know that the ratio of size of image to ratio of size of object is known as magnification , since the magnification is 1 we can conclude that both object and image are of same size as stated above .Here positive sign indicates that the image is virtual and erect.

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