The field of view is maximum for

A person sees his virtual image by holding a mirror very close to the face. When he moves the mirror away from his face, the image becomes inverted. What type of mirror he is using ?

A square $ABCD$ of side $1 \mathrm{mm}$ is kept at distance $15 \mathrm{cm}$ infront of the concave mirror as shown in the figure. The focal length of the mirror is $10 \mathrm{cm}$. The length of the perimeter of its image will be (nearly):

The distance of an object from the focus of a convex mirror of radius of curvature $a$ is $b$. Then the distance of the image from the focus is:

The total internal reflection of a beam of light occurs when beam of light enters-$\left[i_c=\right.$ critical angle, $i=$ angle of incidence$]$