By combination of which processes,a rainbow is formed?

In a laboratory,a material is created with a negative refractive index. $A$ light ray enters from medium $1$ into this material (medium $2$). Which of the following diagrams correctly represents the path of the ray?

To find the focal length of a convex mirror,a student records the following data:

Object Pin	Convex Lens	Convex Mirror	Image Pin
$22.2 \, cm$	$32.2 \, cm$	$45.8 \, cm$	$71.2 \, cm$

The focal length of the convex lens is $f_1$ and that of the mirror is $f_2$. Taking index correction to be negligibly small,$f_1$ and $f_2$ are close to:

If the luminous intensity of a $100 \, W$ unidirectional bulb is $100 \, \text{candela}$, then the total luminous flux emitted from the bulb is ....... $lumen$.

$A$ lamp is hanging $1 \, m$ above the center of a circular table of diameter $1 \, m$. The ratio of illuminances at the center and the edge is:

For a concave mirror, if a virtual image is formed, the graph between $m$ and $u$ is of the form: