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

To determine the available energy for absorption and heating the surface, we need to subtract the reflected solar radiation from the total solar radiation received.

1. Understanding the Concepts:

- Average Solar Radiation: The average amount of solar energy received per unit area per unit time (measured in W/m$^2$).
- Reflected Solar Radiation: The amount of solar energy that is reflected back into space by the Earth's surface and atmosphere (measured in W/m$^2$).
- Absorbed Solar Radiation: The amount of solar energy that is absorbed by the Earth's surface and atmosphere, contributing to heating.

2. Calculation:

The available energy for absorption is the difference between the total solar radiation received and the reflected solar radiation: \[ \text{Absorbed Solar Radiation} = \text{Average Solar Radiation} - \text{Reflected Solar Radiation} \]

3. Given Values:

\( \text{Average Solar Radiation} = 500 \text{ W/m}^2 \)
\( \text{Reflected Solar Radiation} = 70 \text{ W/m}^2 \)

4. Determining the Absorbed Energy:

\[ \text{Absorbed Solar Radiation} = 500 - 70 = 430 \text{ W/m}^2 \]

Final Answer:

The available energy for absorption and heating the surface is 430 W/m$^2$.