Diverging Lens Identification: The Concave Lens

A diverging lens is an optical lens that spreads light rays apart. When parallel rays of light pass through a diverging lens, they are refracted in such a way that they seem to originate from a common point behind the lens. This behavior is characteristic of a specific type of lens.

Understanding Lens Types

Lenses are categorized based on how they refract light. The two primary categories are converging lenses (which bring light rays together) and diverging lenses (which spread light rays apart).

Characteristics of a Diverging Lens

• Spreads Light Rays: The defining feature is its ability to diverge, or spread out, parallel light rays.
• Shape: Typically, a diverging lens is thinner at the center and thicker at the edges.
• Focal Length: The focal length ($f$) of a diverging lens is considered negative ($f < 0$). The focal point is virtual, located where the refracted rays appear to diverge from.

Analyzing the Options

• Plano-Convex Lens: This lens has one flat surface and one convex (outwardly curved) surface. It acts as a converging lens.
• Convex Lens: This lens is curved outwards on both sides (or one side flat and the other convex). It converges parallel light rays to a focal point and is known as a converging lens. Its focal length is positive ($f > 0$).
• Cylindrical Lens: These lenses have a cylindrical shape and focus light onto a line rather than a point. They are used for specific applications like laser line generation, not primarily classified as simple diverging lenses.
• Concave Lens: This lens is curved inwards on both sides (or one side flat and the other concave). It is thinner at the center and thicker at the edges. When parallel light rays pass through it, they diverge. Therefore, the concave lens is known as a diverging lens.

Conclusion

Based on its optical properties of spreading parallel light rays, the concave lens is classified as a diverging lens.