Question

Which one of the following is responsible for attenuation of the incoming solar radiation in the atmosphere?

• A. Absorption
• B. Refraction
• C. Transmission
• D. Diffraction

Hint:

Attenuation means energy is removed from the beam; think about which listed process converts radiant energy into another form rather than just changing its direction or letting it pass.

Answer 1

The Correct Option is A

Step 1: Recall what "attenuation" means for radiation passing through the atmosphere.
As solar (electromagnetic) radiation travels through the Earth's atmosphere, its intensity is reduced, i.e. attenuated, by interactions with atmospheric gas molecules, water vapour, and aerosol/dust particles. This loss of energy from the direct beam is caused mainly by scattering and absorption.
Step 2: Examine each option.
(A) Absorption occurs when constituents such as ozone (\(O_3\), absorbs UV), water vapour and carbon dioxide (absorb in specific infrared bands), and oxygen absorb photons at their characteristic wavelengths and convert that energy into heat; this permanently removes energy from the beam, a direct attenuation mechanism. (C) Transmission is simply the passage of radiation through the atmosphere without being absorbed or scattered; more transmission means LESS attenuation, so it is the opposite effect, not a cause of attenuation. (B) Refraction is the bending of the path of radiation between media of different densities; it changes direction but does not by itself remove energy from the beam. (D) Diffraction is the bending of waves around obstacles or through small apertures; it is not a significant mechanism for atmospheric attenuation of broadband solar radiation.
Step 3: Identify the correct cause of attenuation.
Among the listed options, only absorption genuinely removes energy from the incoming solar beam as it passes through the atmosphere, making the beam weaker by the time it reaches the ground.
Step 4: Conclude.
\[ \boxed{\text{Absorption}} \]