What is the unit of solid angle?

This question was previously asked in
RPF Constable (2018) Official Paper (Held On: 02 Feb 2019)
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  1. Angle
  2. Degree
  3. Stereadian
  4. Andean

Answer (Detailed Solution Below)

Option 3 : Stereadian
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The correct answer is Option 3

Key Points

  •  The unit of solid angle is the steradian (sr).
  • One steradian is defined as the solid angle that, from a point, subtends an area on the surface of a sphere equal to the square of its radius.
  • The steradian is a dimensionless unit, and it is used to measure the extent of a three-dimensional angle or the spread of a beam of radiation or light.
  • For example, a sphere encloses 4π steradians of solid angle, while a cone with a circular base that subtends an angle of one radian at the apex encloses 1 steradian of solid angle.
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