If an object is placed $10 \ cm$ in front of a concave mirror of focal length $20 \ cm,$ the image will be

$A$ concave mirror of radius of curvature $R$ has a circular outline of radius $r$. $A$ circular disc is to be placed normal to the axis at the focus,so that it collects all the light that is reflected from the mirror from a beam parallel to the axis. For $r \ll R$,the area of this disc has to be at least

The sun (diameter $d$) subtends an angle $\theta$ radian at the pole of a concave mirror of focal length $f$. What is the diameter of the image of the sun formed by the mirror?

$A$ concave mirror produces an image of an object such that the distance between the object and the image is $20\ cm$. If the magnification of the image is $-3$,then the magnitude of the radius of curvature of the mirror is: (in $cm$)

The image formed by a convex mirror of a real object is larger than the object:

$A$ short straight object of height $100\, cm$ lies before the central axis of a spherical mirror whose focal length has absolute value $|f|=40\, cm$. The image of the object produced by the mirror is of height $25\, cm$ and has the same orientation as the object. One may conclude from the information: