Name the spherical mirror used as:
$(a)$ $1.$ Shaving mirror,
$2.$ Rear-view mirror in vehicles,
$3.$ Reflector in searchlights.
$(b)$ Write any three differences between a real and virtual image.

$(a)$ $A$ thin converging lens forms a:
$(i)$ Real magnified image.
$(ii)$ Virtual magnified image of an object placed in front of it.
Write the positions of the objects in each case.
$(b)$ Draw labelled ray diagrams to show the image formation in each case.
$(c)$ How will the following be affected on cutting this lens into two halves along the principal axis?
$(i)$ Focal length,
$(ii)$ Intensity of the image formed by half lens.

What is the speed of light waves in a vacuum in units of $km/s$?

The magnification of a real image formed by a concave mirror is always ...

Which lens can be used as a magnifying glass? For which position of the object does a convex lens form:
$(a)$ a virtual and erect image?
$(b)$ a real and inverted image of the same size as that of the object?
Draw labelled ray diagrams to show the formation of the required image in each of the above two cases.

An object is placed at a distance of $18 \ cm$ in front of a concave mirror of focal length $12 \ cm$. Where will the image be formed?