Question

1. A concave mirror of focal length 20cm produce an image of magnification-1, what is the distance of object in front of mirror *

Answer 1

m= -V/U, here V is distance of image, and U is distance of object, m is -1 , -1= -V/U, then U=V , then apply mirror formula, 1/F=1/V+1/U, for concave f is negative, 1/-20= 1/V+1/V, 1/-20= 2/V, V/2= -20, V is -40cm and V=U so object is also -40cm