Focal Length of Spherical Mirrors
The focal length (f) of a spherical mirror is the distance between the pole (P) and the focal point (F). For spherical mirrors, the focal length is related to the radius of curvature (R) by the formula:
f = R/2
When parallel rays of light hit a concave mirror, they converge at the focal point. For a convex mirror, the reflected rays appear to diverge from the focal point behind the mirror.
Mirror Type
Radius of Curvature
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Real-Life Example
Concave mirrors are used in telescopes, satellite dishes, and makeup mirrors. They converge light to a focal point.
Key Points to Remember:
- The focal length (f) is half the radius of curvature (R): f = R/2
- For a concave mirror, the focal point is in front of the mirror
- For a convex mirror, the focal point is behind the mirror (virtual)
- Parallel rays of light converge at the focal point for concave mirrors
- Parallel rays of light appear to diverge from the focal point for convex mirrors