Question

why does the size of the image decrease when you move object from the mirror towards eye

Answer 1

the size of the image decrease when you move object from the mirror towards the eye because the angle made my the object with the eye decreases when you move the object towards the eye

Answer 2

our eyes don't see objects, our eyes receive the incoming light that is reflected off those objects. ... so the angle made the object with they decrease when you more the object towards the eye.