Focal Length of Spherical Mirrors – Class 12 | Chapter – 9 | Physics Short Notes Series PDF for NEET & JEE

Focal Length of Spherical Mirrors: Spherical mirrors are mirrors that have a curved surface that is shaped like a portion of a sphere. There are two types of spherical mirrors: concave mirrors and convex mirrors. When light strikes a spherical mirror, it can be reflected in a specific way depending on the type of mirror and the position of the object relative to the mirror. 

Focal Length of Spherical Mirrors

The focal length of spherical mirror is the distance between the focal point and the pole of the mirror. It is a fundamental property of the mirror that determines how light is reflected and focused by the mirror.

⇒ For a concave mirror, the focal point is located in front of the mirror, and the focal length is a positive quantity. The focal length is equal to half the radius of curvature of the mirror, which can be expressed mathematically as:

f = R/2

where,

• f is the focal length, and
• R is the radius of curvature.

⇒ For a convex mirror, the focal point is located behind the mirror, and the focal length is a negative quantity. The focal length can also be calculated using the radius of curvature, as follows:

f = -R/2

The focal length of spherical mirror is an important property that determines how the mirror reflects and focuses light. Objects that are located beyond the focal point of a concave mirror will produce real, inverted images that are smaller than the original object. Objects that are located within the focal length of a concave mirror will produce virtual, upright images that are larger than the original object. Convex mirrors always produce virtual, upright images that are smaller than the original object, regardless of the location of the object with respect to the mirror.

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By Team Learning Mantras