While performing an experiment of dispersion of white light through a prism, four students represented the dispersion pattern as shown below. Identify the correct representation:

In the following diagram ‘$M$’ is a mirror and ‘$P$’ is an object and ‘$Q$’ is the magnified image of ‘$P$’ formed by the mirror. The mirror ‘$M$’ is a:

The image formation in a convex lens is shown in the following figure.

$\mathrm{AB}$ is the object and ${\mathrm{A}}^{\text{'}}{\mathrm{B}}^{\text{'}}$  is the image. The focal length of the lens is :