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The purpose of this lesson is to explore how our atmosphere interacts with the spectrum of electromagnetic radiation that bombards it from the Sun.
Without the influence of the sun, our planet would be a barren, frozen wasteland. Each day, 1367 Watts / square meter of solar energy hit the top of the atmosphere. Almost 30% of this solar energy will be reflected and scattered back into space (6% by the atmosphere, 20% by clouds, and 4% by the Earth’s surface). About 19% will be absorbed by the atmosphere while the remaining 51% will be absorbed at the Earth’s surface.
Sunlight is a composition of many different wavelengths of light in our visible spectrum, but mostly wavelengths of energy we cannot see. Our Sun actually produces all of the wavelengths of the electromagnetic spectrum. However, due to its surface temperature of 6000°C, the peak visible wavelength emitted by the Sun is 540 nanometers or in the yellow-green part of the visible spectrum, which is why the sun “appears” yellow.
Only certain parts of the electromagnetic spectrum can pass freely through our atmosphere while other forms of radiation are blocked completely. The table below shows the various forms of electromagnetic radiation that are blocked, absorbed, or transmitted by the atmosphere.
| Electromagnetic Radiation | Interaction with Atmosphere | Mechanism that makes this possible |
|---|---|---|
| Gamma Rays | Absorbed | Blocked by ozone and ordinary oxygen |
| X-Rays | Blocked | Blocked by ozone and ordinary oxygen |
| Ultraviolet Rays | Partially absorbed | Absorbed by ozone |
| Visible Light | Transmitted | The atmosphere is transparent to visible light. |
| Infrared Light | Partially absorbed | Absorbed by carbon dioxide and water, the same greenhouse gases that help to warm our planet. |
| Microwaves | Blocked | Blocked by water and carbon dioxide. |
| Radio Waves | Transmitted | The atmosphere is mostly transparent to radio waves. |