Concave lens is also known as Diverging lens because it diverges the light rays that pass through it. This means that the light rays bend away from the principal axis and do not converge at a point after passing through the lens.

Explanation:
A concave lens is a lens that is thinner at the center and thicker at the edges. When parallel rays of light pass through a concave lens, they diverge or spread out. This is because the lens bends the light rays away from the principal axis, which is the imaginary line passing through the center of the lens. The point where the diverging rays appear to come from is called the virtual focus.

The characteristics of a concave lens are opposite to that of a convex lens. A convex lens is thicker at the center and thinner at the edges, and it converges the light rays that pass through it.

The other options mentioned in the question are as follows:

- Converging lens: This term refers to a convex lens that converges the light rays that pass through it.
- Bifocal length: This term refers to the distance between the two focal points of a lens system that has two different focal lengths. Bifocal lenses are commonly used in eyeglasses to correct both near-sightedness and far-sightedness.
- Biconcave lens: This term refers to a concave lens that has two concave surfaces.

Therefore, the correct answer to the question is option B, Diverging lens.

Answer:− B option
Concave lenses are thinner at the middle. Rays of light that pass through the lens are spread out (they diverge). A concave lens is a diverging lens.