Question

An object 4 cm high is placed at a distance of 6 cm in front of a
concave mirror of focal length 12 cm. Find the position of the image

Answer 1

Given :
object distance= -6cm [sign convention]
focal length=f=-12cm
Image distance=V=?
by mirror formula:
1/f=1v+1/u
1/v=1/f-1/u
=-1/12+1/6
=-1+2/12
=1/12
=12
v=12cm
when an object is placed at a distance of 6cm [in between p and F]. we get image behind mirror.

Answer 2

Given
after sign conventions
f=-12cm
u=-6cm
ho=4cm
by mirror formula
1/f=1/v+1/u
1/v=1/f-u/u
=1/-12+1/6
-1/12+1/6
1/12
since object is placed between p and F we get virtual and erect
m=v/u
=-12/-6
=+2
also m=hig/ho
2hig/4cm
hi =8cm