Spherical lenses are optical devices made from transparent materials, shaped like a portion of a sphere. They can be either convex, which bulges outward, or concave, which curves inward. These lenses are used to focus or disperse light, making them essential in various applications like glasses, cameras, and microscopes. The curvature of a spherical lens determines how it bends light. Convex lenses converge light rays to a point, useful for magnifying images, while concave lenses diverge light rays, often used to correct nearsightedness. Understanding these properties helps in designing effective optical systems in fields like photography and optometry.