SSC Selection Post 2022 PYQ — Question 46

The correct answer is option 3 i.e. solid-angle measure.

In physics, the steradian (sr) is indeed the SI unit of solid angle. It's the three-dimensional equivalent of the radian, which measures plane angles.One steradian is defined as the solid angle subtended at the center of a sphere by a portion of its surface whose area is equal to the square of the sphere's radius (A=r2). The entire surface of a sphere subtends a solid angle of 4π steradians at its center. It's crucial in fields like optics and radiation.