Correct Answer  Option 4 : 120 cm
CONCEPT:
Mirror
 A mirror is a polished surface that reflects the light incident on it.
 Types of the mirror:
 Plane mirror

Spherical mirror
 Concave mirror
 Convex mirror
Mirror formula:
 The expression which shows the relation between object distance (u), image distance (v), and focal length (f) is called the mirror formula.
\(⇒\frac{1}{v} + \frac{1}{u} = \frac{1}{f}\)
Linear magnification (m):
 It is defined as the ratio of the height of the image (hi) to the height of the object (ho).
\(⇒ m=\frac{h_{I}}{h_{O}}=\frac{v}{u}\)
CALCULATION:
Given f = 80 cm, and \(\frac{h_{i}}{h_{o}}=2\)
Where hi = height of the image, and ho = height of the object
 The magnification of the mirror is given as,
\(⇒ m=\frac{h_{I}}{h_{O}}=\frac{v}{u}\)
\(⇒ v=u×\frac{h_{i}}{h_{o}}\)
\(⇒ v=u×\frac{(2)}{1}\)
⇒ v = 2u (1)
According to the mirror formula,
\(⇒ \frac{1}{f}=\frac{1}{u}+\frac{1}{v}\) (2)
Where u = distance of the object from the mirror, v = distance of the image from the mirror, and f = focal length
By equation 1 and equation 2,
\(⇒ \frac{1}{f}=\frac{1}{u}+\frac{1}{2u}\)
\(⇒ \frac{1}{80}=\frac{3}{2u}\)
⇒ u = 120 cm
 Hence, option 4 is correct.