Kahjin’s Weblog


Posted in 未分類 by kahjin on 4月 11, 2008


Wavelength can greatly influence how a wave interacts with matter—how well it is transmitted, absorbed, reflected, or diffracted. For example, the ways in which shock waves of different wavelengths travel through and reflect from layers of rock are an important clue as to what the interior of the earth is like. The interaction of electromagnetic waves with matter varies greatly with wavelength, both in how they are produced and in what their effects are. Different but somewhat overlapping ranges have been given distinctive names: radio waves, microwaves, radiant heat or infrared radiation, visible light, ultraviolet radiation,x rays, and gamma rays.




Materials that allow one range of wavelengths to pass through them may completely absorb others. For example, some gases in the atmosphere, including carbon dioxide and water vapor, are transparent to much of the incoming sunlight but not to the infrared radiation from the warmed surface of the earth. Consequently, heat energy is trapped in the atmosphere. The temperature of the earth rises until its radiation output reaches equilibrium with the radiation input from the sun. Another atmospheric gas, ozone, absorbs some of the ultraviolet radiation in sunlight—the wavelengths that produce burning, tanning, and cancer in the skin of human beings.




Even within the named ranges of electromagnetic radiation, different wavelengths interact with matter in different ways. The most familiar example is that different wavelengths of visible light interact with our eyes differently, giving us the sensation of different colors. Things appear to have different colors because they reflect or scatter visible light of some wavelengths more than others, as in the case of plants that absorb blue and red wavelengths and reflect only green and yellow. When the atmosphere scatters sunlight—which is a mixture of all wavelengths—short-wavelength light (which gives us the sensation of blue) is scattered much more by air molecules than long-wavelength (red) light is. The atmosphere, therefore, appears blue and the sun seen through it by unscattered light appears reddened.


1*感覚的に”宿る”を選択した。後で、appearの意味を調べると、to come into exsistenceという意味もあった。




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