$A$ bulb of $100 \text{ W}$ is hanging at a height of $1 \text{ m}$ above the centre of a circular table of diameter $4 \text{ m}$. If the intensity at a point on its rim is $I_0$,then the intensity at the centre of the table will be:

$A$ glass beaker has a solid,plano-convex base of refractive index $1.60$,as shown in the figure. The radius of curvature of the convex surface $(SPU)$ is $9 \ cm$,while the planar surface $(STU)$ acts as a mirror. This beaker is filled with a liquid of refractive index $n$ up to the level $QPR$. If the image of a point object $O$ at a height of $h$ ($OT$ in the figure) is formed onto itself,then which of the following option$(s)$ is (are) correct?
$(A)$ For $n=1.42, h=50 \ cm$
$(B)$ For $n=1.35, h=36 \ cm$
$(C)$ For $n=1.45, h=65 \ cm$
$(D)$ For $n=1.48, h=85 \ cm$

$A$ point object $O$ is moving towards a concave mirror as shown in the figure. Choose the correct option representing the direction of the velocity of the image ($F$ is the focus and $C$ is the centre of curvature).

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:

The exposure time of a camera lens at the $f/2.8$ setting is $1/200$ second. The correct time of exposure at $f/5.6$ is......$sec$

What is an image? Explain its types.