Lenses: Convex and Concave

What is a Lens?

A lens is a piece of transparent material (like glass or plastic) with curved surfaces. Unlike mirrors which reflect light, lenses allow light to pass through them (refraction).

Types of Lenses

1. Convex Lens:

   • Thicker in the middle than at the edges.
   • It is a Converging Lens (bends light inwards).
   • Image: Can be Real or Virtual, Enlarged or Diminished, depending on distance.
   • Activity: It can burn paper by focusing sunlight (similar to a concave mirror).

2. Concave Lens:

   • Thicker at the edges than in the middle.
   • It is a Diverging Lens (spreads light outwards).
   • Image: Always Virtual, Erect, and Diminished.

Applications of Lenses

• Convex Lens: Magnifying glasses, cameras, human eye, microscopes, telescopes.
• Concave Lens: Peepholes in doors, correction for short-sightedness (myopia).