$A$ concave mirror gives an image three times as large as the object placed at a distance of $20\,cm$ from it. For the image to be real,the focal length should be........$cm$

$A$ small rod of length $2 \, mm$ lies along the principal axis at a distance of $30 \, cm$ from a concave mirror of focal length $20 \, cm$. The axial length of the image of the rod is.....$mm$.

$A$ boy stands straight in front of a mirror at a distance of $30 \ cm$ away from it. He sees his erect image whose height is $\frac{1}{5}$ of his real height. The mirror he is using is

$A$ square wire frame of side length $3.0 \, cm$ is placed $25 \, cm$ away from a concave mirror of focal length $10 \, cm$. The center of the wire frame is on the axis of the mirror,with two of its sides perpendicular to the axis. The area of the image will be $..... \, cm^2$.

The direction of a ray of light incident on a concave mirror is shown by $PQ$,while the directions in which the ray would travel after reflection are shown by four rays marked $1, 2, 3,$ and $4$. Which of the four rays correctly shows the direction of the reflected ray?

$A$ concave mirror is used to focus the image of a flower on a nearby wall $120 \ cm$ from the flower. If a lateral magnification of $16$ is desired,the distance of the flower from the mirror should be $... \ cm$.