4. In what portion of the electromagnetic spectrum does the sun emit its peak ra

Question

4. In what portion of the electromagnetic spectrum does the sun emit its peak radiant energy? In what portion of the electromagnetic spectrum does the Earth emit its peak radiant energy (see Table 1)? Wavelength (um-10m-micrometer) c0.0001 0.0001 to 0.01 0.01 to 0.4 Type of Energy Gamma X-ray Ultraviolet (UV) Visible Near Infrared (Near IR) Thermal Infrared Microwave Radio 0.4 to 0.7 0.7 to 4.0 4 to 100 100 to 1,000,000 (1 m) 1,000,000 (1 m) Part II: Radiation Flux Behavior and Observations Incoming and outgoing shortwave (White) and longwave (Gray) describe the four fundamental types of radiation fluxes (see Figure 1, pg. 6). 1) Incoming shortwave radiation (SW+) is the amount of global shortwave radiation received at the surface. It depends on location (eg, polar locations receive less direct sunlight), time of year (eg., sunlight is less direct in winter and more direct in the summer), time of day (eg., sunlight is most intense around noon), cloudiness (which may reflect sunlight away before it reaches the surface) and other atmospheric conditions Some of the solar radiation that reaches the surface is reflected away as outgoing shortwave radiation (SW). Note that this is not to be confused with the amount of sw reflected away (or absorbed or scattered) before it reaches the surface (eg, by clouds). It depends on a surface characteristic known as albedo, which is dependent on the color and texture of the surface (eg., a white, snow covered surface has high 2)

Explanation / Answer

Over 99% of the energy flux raduated by the sun lies in the range from 0.15 to 4 micrometre. Approximately 50% lies in the visible region from 0.4 to 0.7 micrometre. The solar spectrum peaks at 0.49 pm, the green part of the visible portion.

About 99% of the radiation from the sun has wavelength in the range from 4 micrometre to 100 micrometre, in the thermal infrared portion of the electromagnetic spectrum. Wavelengths larger than 40 micrometre are usually neglected because of their small contribution, hence wavelengths only upto 50 micrometre are considered.

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