The convergence of a concave mirror can be decreased by dipping it in which of the following?

$A$ mobile phone lies along the principal axis of a concave mirror,as shown in the figure. Show by a suitable diagram,the formation of its image. Explain why the magnification is not uniform. Will the distortion of the image depend on the location of the phone with respect to the mirror?

At what distance in front of a concave mirror of focal length $30\; cm$,should an object be placed (in $cm$) so that its real image of size three times that of the object is obtained?

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

$A$ convex mirror has a radius of curvature of $22 \; cm$. If an object is placed $14 \; cm$ away from the mirror,then its image is formed at:

An object of length $6 \ cm$ is placed on the principal axis of a concave mirror of focal length $f$ at a distance of $4f$. The length of the image will be......$cm$.