Answer:
18. a
20. a
21. b
22. c
Explanation:
18. The earth's orbit around the sun is not circular but is elliptical with an average distance between the earth and the sun being about 92,955,807 miles.
19. The year 2019 is a year of solar minimum in the solar cycle as in this year the sun remains quite 62% of the time(with the absence of any sunspot movement). We are arriving at a new low of 200 years in sunspot exercises.
20. Hotter objects in the electromagnetic spectrum produce a greater amount of their light at short wavelengths, and cold objects emits a greater amount of their light at long wavelengths.
21. The sun's energy reaches the earth with the major part of this energy lying in the Visible region.
22. Once in the Earth's air, mists and the surface assimilate the sun oriented vitality. The ground warms up and re-discharges vitality as long wave radiation as infrared beams.
Earth transmits long wave radiation since Earth is cooler than the sun and has less energy accessible to emit.