Sun is the main source of energy on the Earth. Life sustains on the Earth because of electromagnetic radiations and without the Sun, the Earth would have 270 degree Celsius of equilibrium temperature. The Earth emits an equal amount of energy as it receives from the space, so there is a heat balance on the Earth. The Sun pours a huge quantity of electromagnetic energy on it and everything on the Sun is the source of these radiations. The Sun emits over a wide range of electromagnetic radiations. The incident solar energy, mainly, is in the visible part of the solar spectrum, while the key part of the radiation lies in the infrared region.
In eight minutes the radiation emitted from the Sun gets to the Earth. The ray which lightens up the surface of the Earth is the visible light, also known as white light, which is the continuous mixture of colors. This light when passed through the prism disperses into a band of seven colors. The energetic part of the spectrum is the ultraviolet radiation, which is undetectable having shorter wavelengths compared to white light. Those of ultraviolet radiations having extremely shorter wavelengths are filtered in the outer atmosphere by the ozone layer.
Thermal radiations, as they are referred to, are the invisible infrared radiations having longer wavelengths compared to those of white light. Mostly, the incoming infrared rays are filtered by the atmosphere of the Earth containing water vapors. The opacity of the atmosphere, chiefly, is responsible for maintain the warmth of the Earth, although the surface of the Earth is rather transparent to the longer wavelengths in the infrared region.
Besides optical radiations from the Sun, solar energy spectrum contains radio and X-rays also. Hotter bodies emit a larger wavelength of spectrum. Intense radio waves have been observed over the Sun's surface at 330 MHz having wavelength of about one meter. The studies of wavelength in the X-rays component of the electromagnetic spectrum are made by specially designed sensitive imaging techniques.
In eight minutes the radiation emitted from the Sun gets to the Earth. The ray which lightens up the surface of the Earth is the visible light, also known as white light, which is the continuous mixture of colors. This light when passed through the prism disperses into a band of seven colors. The energetic part of the spectrum is the ultraviolet radiation, which is undetectable having shorter wavelengths compared to white light. Those of ultraviolet radiations having extremely shorter wavelengths are filtered in the outer atmosphere by the ozone layer.
Thermal radiations, as they are referred to, are the invisible infrared radiations having longer wavelengths compared to those of white light. Mostly, the incoming infrared rays are filtered by the atmosphere of the Earth containing water vapors. The opacity of the atmosphere, chiefly, is responsible for maintain the warmth of the Earth, although the surface of the Earth is rather transparent to the longer wavelengths in the infrared region.
Besides optical radiations from the Sun, solar energy spectrum contains radio and X-rays also. Hotter bodies emit a larger wavelength of spectrum. Intense radio waves have been observed over the Sun's surface at 330 MHz having wavelength of about one meter. The studies of wavelength in the X-rays component of the electromagnetic spectrum are made by specially designed sensitive imaging techniques.
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