If a lens has a focal length of -20 cm, what type of lens is it?

If a lens has a focal length of -20 cm, what type of lens is it?

Step 1: Understand what focal length means. Focal length is the distance from the lens to the point where light rays converge or appear to diverge.
Step 2: Identify the sign of the focal length. A positive focal length indicates a converging lens (like a convex lens), while a negative focal length indicates a diverging lens.
Step 3: Since the given focal length is -20 cm, it is negative.
Step 4: Conclude that a negative focal length means the lens is a concave lens, which diverges light rays.

Focal Length – The distance from the lens to the focal point; negative values indicate a concave lens.
Types of Lenses – Lenses can be classified as concave (negative focal length) or convex (positive focal length).