Question

an object is placed at a distance of 10 cm from a concave mirror of focal length 20 cm find the image distance and nature of the image

Answer 1

1/f = 1/v+ 1/u
1/-20= 1/-10+ 1/v
1/-20 - 1/ -10 = 1/v
1 -20+ 1/10 = 1/v
-1 + 2/20 =1/v
1 /20 = 1/v

v = 20 cm
the image will be virtual nd errect