For a concave mirror,the minimum distance between a real object and its real image is ...........

$A$ concave mirror for face viewing has a focal length of $0.4\,m$. The distance at which you hold the mirror from your face in order to see your image upright with a magnification of $5$ is......$m$.

An object is placed at a distance of $18 \ cm$ in front of a mirror. If the image is formed at a distance of $4 \ cm$ on the other side,then the focal length,nature of the mirror,and nature of the image are respectively:

$A$ rod of length $10 \text{ cm}$ lies along the principal axis of a concave mirror of focal length $10 \text{ cm}$ as shown in the figure. The length of the image is . . . . . . $\text{cm}$.

$A$ convex lens (of focal length $20\, cm$) and a concave mirror,having their principal axes along the same lines,are kept $80\, cm$ apart from each other. The concave mirror is to the right of the convex lens. When an object is kept at a distance of $30\, cm$ to the left of the convex lens,its image remains at the same position even if the concave mirror is removed. The maximum distance of the object for which this concave mirror,by itself,would produce a virtual image would be.....$cm$.

The image formed by a convex mirror is always: