Why don't all wavelengths of the sun's radiation reach Earth's surface and Earth and Sun emit radiation but they do so at largely different wavelengths?
The Earth's atmosphere acts as a filter, allowing some wavelengths of radiation to pass through while blocking others. This is why we only see a certain range of colors when we look up at the sky. The shorter wavelengths of radiation, such as ultraviolet and X-rays, are absorbed by the ozone layer, which is a layer of gas in the atmosphere that is made up of ozone molecules. These molecules absorb these types of radiation and prevent them from reaching the Earth's surface.
The longer wavelengths of radiation, such as visible light and infrared radiation, are able to pass through the atmosphere and reach the Earth's surface. Visible light is the type of radiation that allows us to see. Infrared radiation is a type of radiation that we cannot see, but we can feel it as heat.
The Earth and the Sun emit radiation at different wavelengths because they have different temperatures. The Sun is much hotter than the Earth, so it emits radiation at shorter wavelengths. The Earth is cooler than the Sun, so it emits radiation at longer wavelengths.
Not all radiation emitted from the sun reaches Earth's surface. Much of it is absorbed, reflected or scattered in the atmosphere. At the surface, solar energy can be absorbed directly from the sun, called direct radiation, or from light that has been scattered as it enters the atmosphere, called indirect radiation. The earth's atmosphere absorbs the majority of ultraviolet, X-, and gamma rays, which are all shorter wavelengths than visible light. High energy X- and gamma rays would damage organisms and cells of creatures if they were to reach the earth's surface directly. Fortunately, the atmosphere protects life on earth. Ultraviolet radiation is mostly blocked by the ozone layer of Earth's atmosphere, but a small fraction of ultraviolet rays from our Sun do penetrate to cause sunburn or, in extreme cases of overexposure, skin cancer in human beings. The Earth absorbs most of the energy reaching its surface, a small fraction is reflected. In total approximately 70% of incoming radiation is absorbed by the atmosphere and the Earth's surface while around 30% is reflected back to space and does not heat the surface. Snow and ice, airborne particles, and certain gases have high albedos and reflect different amounts of sunlight back into space. Low, thick clouds are reflective and can block sunlight from reaching the Earth's surface, while high, thin clouds can contribute to the greenhouse effect. Since there is no medium between the surface of Earth and Sun, heat transfer through conduction is not possible. Radiation is the method of heat transmission that occurs without the help of a medium. So, we can say that the heat from the Sun reaches the Earth through radiation.Now 110 parts leaves the surface as infrared radiation, as long wave radiation, emitted from the surface, but doesn't make it out to space because it's actually absorbed by greenhouse gases in the atmosphere. UVC rays do not reach the Earth's surface because they are completely absorbed by the atmosphere. The Earth radiates energy at wavelengths much longer than the Sun because it is colder. Part of this long wave radiation is absorbed by greenhouse gases which then radiate energy into all directions, including downwards and thereby trapping heat in the atmosphere. The Sun emits radiation at a shorter wavelength than the Earth because it has a higher temperature and Planck's curve for higher temperatures peaks at shorter wavelengths. It is for this reason that Earth's radiation is referred to as long wave and the Sun's radiation is shortwave. However, 99 per cent of the energy of solar radiation is contained in the wavelength band from 0.15 to 4 μm, comprising the near ultraviolet, visible and near infrared regions of the solar spectrum, with a maximum at about 0.5 μm.Some wavelengths of electromagnetic waves arriving from space are absorbed by the atmosphere and never reach the surface of our planet. Take a look at the following diagram. The earth's atmosphere absorbs the majority of ultraviolet, X-, and gamma rays, which are all shorter wavelengths than visible light.
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