|A lens which is thick (bulged) in the middle but thin (tapered) at the edges is called convex lens.
|A lens which is thin in the middle but thick at the edges is called a concave lens.
|It converges the parallel beam of light falling on it, hence also called a converging lens.
|It diverges a parallel beam of light falling on it, hence also called a diverging lens.
|It has a real focus.
|It has a virtual focus.
|The power of this lens is positive.
|The power of this lens is negative.
|It forms a real or virtual image depending on the position of the object.
|It always forms a virtual image.
|It is used in the correction of long-sightedness.
|It is used in the correction of short-sightedness.