Question

What is the focal power of a spherical mirror or lens? What may be the reason for using \[P{\text{ }} = {\text{ }}\dfrac{1}{f}\]as its expression?

Answer 1

Hint:A spherical mirror is one that is shaped like a fragment cut from a spherical surface. Concave and convex spherical mirrors are the two varieties of spherical mirrors.A lens is a transmissive optical instrument that uses refraction to concentrate or scatter a light ray. A clear lens is made up of a single transparent piece of glass.

Complete answer:
A spherical mirror is one that is shaped like a fragment cut from a spherical surface. Concave and convex spherical mirrors are the two varieties of spherical mirrors. A lens is a transmissive optical instrument that uses refraction to concentrate or scatter a light ray. A clear lens is made up of a single transparent piece of glass.

The focal length of an optical system is the opposite of the system's optical power; it measures how intensely the system converges or diverges light. A device with a positive focal length converges light, while one with a negative focal length diverges light.The inverse of the focal length is used to calculate a lens' power. Dioptres are a unit of measurement for lens strength (D). Diverging (concave) lenses have negative focal lengths, but their power levels are negative.

The degree to which a lens or mirror diverges or converges light is known as the focal power of a spherical mirror or lens. The inverse of the focal length of a mirror or telescope is the power of the lens or mirror. When the focal length is long, the lens or mirror's power is low.Hence, \[P{\text{ }} = {\text{ }}\dfrac{1}{f}\] is used as the expression.

Note:The focal length of an optical system is the opposite of the system's optical power; it measures how intensely the system converges or diverges light. A device with a positive focal length converges light, while one with a negative focal length diverges light.