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

In an experiment to determine the focal length $(f)$ of a concave mirror by the $u-v$ method,a student places the object pin $A$ on the principal axis at a distance $x$ from the pole $P$. The student looks at the pin and its inverted image from a distance keeping his/her eye in line with $PA$. When the student shifts his/her eye towards left,the image appears to the right of the object pin. Then,

$A$ 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 ...... $cm$.

As the position of an object $(u)$ reflected from a concave mirror is varied,the position of the image $(v)$ also varies. By letting the $u$ change from $0$ to $+\infty$,the graph between $v$ versus $u$ will be:

$A$ convex mirror of focal length $10\,cm$ is shown in the figure. $A$ linear object $AB = 5\,cm$ is placed along the optical axis. Point $B$ is at a distance of $20\,cm$ from the pole of the mirror. Then,the size of the image of $AB$ will be:

The image formed by a convex mirror of focal length $f$ is $(1/n)$ times the size of the object. The distance of the object from the mirror is: