Thinner in the center that at the edges; virtual image smaller.

lens

concave mirror

concave lenses

convex lens

The correct answer is concave lenses.

Explanation:

A concave lens refers to a lens, which exhibits at least one surface that bends inwardly. It is a diverging lens, which signifies that it disperses out the light rays that have been refracted via it. A concave lens is thinner at its midpoint in comparison to its edges and has an application in correcting short-sightedness.  

The formation of an image by a concave lens is virtual, which signifies that it will seem to be farther away than it actually is, and thus, smaller in comparison to the object itself.  

while cooking a piece of 1/2 pound beef steak, a cast iron pan (2.4kg in weight) was heated 260 celsius.