The magnification (m) and focal length (f) of a plane mirror are

The correct answer is Option (2) → \( m = +1;\ f = \infty \)

A plane mirror forms a virtual, erect image of the same size as the object, so the magnification is \( m = +1 \).

A plane mirror can be treated as a spherical mirror of infinite radius of curvature, so

    \( \displaystyle f = \frac{R}{2} = \frac{\infty}{2} = \infty \)

The image is upright (positive sign) and parallel rays stay parallel after reflection, which is why the focal length is infinite, not zero.