Question

Path length of radiation through the atmosphere to the length of path when the sun is at zenith is called ___________

(a) Declination

(b) Air mass

(c) Azimuth

(d) Solar Constant

I had been asked this question during an interview.

The query is from Solar Constant in section Solar Energy of Energy Engineering

Answer 1

Correct answer is (b) Air mass

To elaborate: Path length of radiation through the atmosphere to the length of path when the sun is at zenith is called Air mass.

  Air mass, m = Cos (altitude angle), except for very low solar altitude angles.

      m = 1; When the sun is at the zenith

      m = 2; When zenith angle is 60^o

      m = 3; sec (θz) for m>3.