The focal length of a convex mirror whose radius of curvature is 30cm will be:

  1. 30 cm 
  2. 60cm
  3. 15cm
  4. 7.5 cm

Answer (Detailed Solution Below)

Option 3 : 15cm
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Detailed Solution

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CONCEPT:

  • Convex mirror: It is an outward curved mirror that produces a diminished image.
    • Convex mirrors either diverge a parallel beam of light into all directions or gather light from all directions and produce a parallel beam out of it.
  • Focal length (f): The distance between the centre of the mirror and the focal point (where parallel rays of light meet or appear to meet) of the mirror is called the focal length.
  • The radius of curvature (R): The distance between the centre of the lens or mirror to the vertex which is located on the local optical axis is called the Radius of Curvature.
  • The focal length is half of the radius of curvature.

f = R/2

CALCULATION:

Given that:

Radius of curvature (R) = 30 cm,

The focal length (f) = R/2 = 30/2 = 15 cm

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