$A$ convex lens of focal length $10 \ cm$ is placed at a distance of $12 \ cm$ from a wall. How far from the lens should an object be placed so as to form its real image on the wall (in $cm$)?

In which of the following,the image of an object placed at infinity will be highly diminished and point-sized?

What can be said about the magnification of an image formed by a convex mirror?

$(i)$ Describe an activity to find the approximate value of the focal length of a concave mirror.
$(ii)$ What happens to the size of the image of an object when it is moved gradually away from a convex mirror?
$(iii)$ In an experiment to study refraction through a glass slab,it is observed that a ray of light undergoing refraction emerges parallel to the direction of the incident ray. Why does it happen so? Explain with the help of a diagram.

$(a)$ Write any three differences between concave and convex mirror.
$(b)$ Draw ray diagram to show what happens to a ray of light after reflection from a convex mirror,if it
$(i)$ is incident parallel to principal axis.
$(ii)$ incident at the pole.

$A$ ray of light $XY$ is incident on a mirror as shown in the figure. The angle of incidence for this ray is the angle between it and the line joining two other points in the figure. Name these two points and show the course of rays after reflection.