How many centres of curvature does a lens have?

Rays from the Sun converge at a point $15 \, cm$ in front of a concave mirror. Where should an object be placed so that the size of its image is equal to the size of the object?

For driving a car,what type of mirror would you prefer to see the traffic at your back and why?

What are the advantages and disadvantages of using a convex mirror for seeing traffic at the rear?

Where should an object be placed so that a real and inverted image of the same size is obtained by a convex lens?

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