Question

If the average solar radiation received by the earth is 500 W/m$^2$ and reflects 70 W/m$^2$, what is the available energy for absorption and heating the surface?

• A. 500 W/m$^2$
• B. 70 W/m$^2$
• C. 430 W/m$^2$
• D. 570 W/m$^2$

Hint:

• Energy absorbed by a surface = Total incoming energy - Energy reflected by the surface.
• The fraction of energy reflected is related to the surface's albedo.
• In this case: Absorbed Energy = $500 \text{ W/m}^2 - 70 \text{ W/m}^2 = 430 \text{ W/m}^2$.
• This absorbed energy is what causes the surface to heat up.

Answer 1

The Correct Option is C

The interaction of solar radiation with the Earth's surface involves several processes:

• Incoming Solar Radiation (Insolation): The total amount of solar energy received by the surface.
• Reflection (Albedo): A portion of the incoming solar radiation is reflected back to space by the surface. The reflectivity of a surface is called its albedo.
• Absorption: The portion of the incoming solar radiation that is not reflected is absorbed by the surface. This absorbed energy heats the surface.
• Transmission (less relevant for opaque surfaces like land): Some radiation might pass through transparent or translucent materials.

The energy available for absorption and heating the surface is the incoming solar radiation minus the reflected solar radiation. Given: Average solar radiation received (Incoming) = 500 W/m$^2$ Reflected solar radiation = 70 W/m$^2$ Available energy for absorption and heating = Incoming Radiation - Reflected Radiation Available energy = 500 W/m$^2$ - 70 W/m$^2$ Available energy = 430 W/m$^2$ Option (a) is the total incoming radiation. Option (b) is the reflected radiation. Option (d) is the sum of incoming and reflected, which is incorrect. \[ \boxed{\text{430 W/m}^2} \]