The light rays entering the diverging lens parallel to its axis diverge, and all rays seem to originate from its focal point F. But the dashed line is not a light, but rather indicates the direction in which it appears. The focal length f of a divergent lens is negative.

A concave lens is a divergent lens because it bends (diverges) light from its axis. In this case, the shape of the lens should be such that all light rays incident parallel to its axis appear to come from the same point F, which is defined as the focal point of the diverging lens. The distance from the center of the lens to the focal point is once again referred to as the focal length f. Note that the focal length and refractive power of a divergent lens are defined as negative.

A concave lens has a divergent effect on light, which can be simply understood as the outward divergence of light. However, if the incident light is already a converging light and the degree of divergence of light from a concave lens is not as high as the degree of convergence of light, then the emitted light is still converging (but the degree of convergence will be reduced).