Introduction:
Lenses are transparent objects made of glass or plastic that are used to refract light. They are commonly used in various optical devices such as cameras, eyeglasses, and microscopes. There are two main types of lenses: concave and convex lenses. These lenses have different shapes and properties which result in different optical effects. Let's explore the characteristics of these lenses in detail.

Concave Lens:
A concave lens, also known as a diverging lens, is thinner at the center and thicker at the edges. It has a curved surface that bulges inward. When light passes through a concave lens, it diverges or spreads out. The lens causes parallel light rays to bend away from the principal axis, the imaginary line passing through the center of the lens.

Properties and Uses of Concave Lens:
- Shape: Concave lenses have a curved surface that bulges inward, giving them a thinner center and thicker edges.
- Focal Length: The focal length of a concave lens is negative, denoted as (-f). The distance from the lens to the focal point is measured as -f.
- Divergence of Light: When parallel light rays pass through a concave lens, they diverge or spread out. This property makes concave lenses useful for creating virtual images, correcting nearsightedness, and in devices like projectors and cameras.
- Virtual Images: Concave lenses can create virtual images, which are formed on the same side as the object. These images are always upright and smaller than the object.
- Nearsightedness Correction: Concave lenses are commonly used to correct nearsightedness or myopia. They help in diverging the light entering the eye, allowing it to focus correctly on the retina.

Convex Lens:
A convex lens, also known as a converging lens, is thicker at the center and thinner at the edges. It has a curved surface that bulges outward. When light passes through a convex lens, it converges or comes together. The lens causes parallel light rays to bend towards the principal axis.

Properties and Uses of Convex Lens:
- Shape: Convex lenses have a curved surface that bulges outward, giving them a thicker center and thinner edges.
- Focal Length: The focal length of a convex lens is positive, denoted as (+f). The distance from the lens to the focal point is measured as +f.
- Convergence of Light: When parallel light rays pass through a convex lens, they converge or come together. This property makes convex lenses useful for creating real images, magnifying objects, and in devices like telescopes and magnifying glasses.
- Real Images: Convex lenses can create real images, which are formed on the opposite side of the object. These images can be both inverted and magnified, depending on the object's position.
- Magnification: Convex lenses are commonly used to magnify objects. The image formed by a convex lens can be larger or smaller than the object, depending on the distance between the object and the lens.

Conclusion:
In summary, concave and convex lenses