An object is placed at $20 \ cm$ in front of a concave mirror,which produces a three times magnified real image. What is the focal length of the concave mirror (in $cm$)?

$A$ small linear object is placed on the optical axis of a concave mirror. If the distance of the nearest end of the object from the mirror is greater than the radius of curvature,then:

An object is placed beyond the centre of curvature $C$ of a concave mirror. If the distance of the object is $d_{1}$ from $C$ and the distance of the image formed is $d_{2}$ from $C$,the radius of curvature of this mirror is

When an object is placed at a distance of $25 \ cm$ from a concave mirror,the magnification is $m_1$. The object is moved $15 \ cm$ farther away with respect to the earlier position and the magnification becomes $m_2$. If $m_1/m_2 = 4$,the focal length of the mirror is $....... \ cm$ (Assume image is real and $m_1, m_2$ are numerical values).

$A$ beam of light is converging towards a point $O$ behind a convex mirror of focal length $20 \, cm$. If the point $O$ is $10 \, cm$ behind the mirror,then the position of the image is at a distance of ..... $cm$.

$A$ person looks at the image of two parallel finite length lines $PQ$ and $RS$ in a convex mirror (see figure). Which of the following represents schematically the image correctly? Note: Letters $P, Q, R$ and $S$ are used only to denote the endpoints of the lines.