What type of lens behaviour will an air bubble inside water show?

$A$ concave mirror can be used to obtain a parallel beam of light from a small lamp.

Magnification produced by a rear-view mirror fitted in vehicles $....$

$A$ 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 $cm$)?

What is the nature of the final image formed by an astronomical telescope compared to the object?

What type of mirror is used to obtain a real image?