Question

When an object is at a distance x1 and x2 from the poles of a concave mirror, images of same magnification are formed. The magnitude of focal length of the mirror is ?
a) (x1 +x2)/2
b) (x1 - x2)/2
C) x1 + x2
D) x1 - x2

Answer 1

Given,
Object distance, u=-(x1 +f)
Image distance, v= -(x2 +f)
Focal length,F=-f
Using mirror formula,
1/v + 1/u=1/F
-1/(x2 +f) - 1/ (x1 +f)=-1/f
On solving, we get
f=x1x2−−−−√

I hope it will help you