a)Around 1/3rd of solar radiation is: -
i) IR rays
ii) IM rays
iii)ID rays iv)IF rays
Answers
Answer:
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Explanation:
Solar radiations are becoming increasingly appreciated because of their influence on living matter and the feasibility of its application for useful purposes. It is a perpetual source of natural energy that, along with other forms of renewable energy, has a great potential for a wide variety of applications because it is abundant and accessible. Solar radiation is rapidly gaining ground as a supplement to the nonrenewable sources of energy, which have a finite supply. The electromagnetic radiation emitted by the sun covers a very large range of wavelengths, from radiowaves through the infrared, visible and ultraviolet to X-rays and gamma rays. 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. About 40 per cent of the solar radiation received at the earth’s surface on clear days is visible radiation within the spectral range 0.4 to 0.7 μm, while 51 per cent is infrared radiation in the spectral region 0.7 to 4 μm.
The total radiation emitted by the sun in unit time remains practically constant. The variations actually observed in association with solar phenomena like sunspots, prominences and solar flares are mainly confined to the extreme ultraviolet end of the solar spectrum and to the radiowaves. The contribution of these variations to the total energy emitted is extremely small and can be neglected in solar energy applications. The planet earth revolves around the sun in an elliptical orbit of very small eccentricity with the sun at one of the foci, completing one revolution in one year. The axis of rotation of the earth is inclined at about 23½ degrees with respect to the plane of orbital revolution and is directed always to a fixed point in space. As a consequence of this geometry of the sun and the earth, large seasonal variations occur in the amount of solar radiation received at different latitudes of the earth. The largest annual variations occur near the two poles and the smallest near the equator. During the course of its annual motion around the sun in an elliptical orbit, the earth comes nearest to the sun each year around January 5 (perihelion) and farthest around July 5 (aphelion). The sun-earth distance at perihelion is 1.471 × 108 km and at aphelion 1.521 × 108 km. The mean distance is 1.496 × 108 km, which is known as 1 Astronomical Unit. Due to the variations in the sun-earth distance, the solar radiation intercepted by the earth varies by ±3.3 per cent around the mean value, being maximum at the beginning of January and minimum at the beginning of July.
Of the entire quantity of radiant energy emitted by the sun’s spherical surface, only a small fraction (4.5 × 10−10) is actually intercepted by the planet earth. The amount of solar energy falling in unit time on unit area, held normal to the sun’s rays outside the earth’s atmosphere when the earth is at the mean distance from the sun, is called the solar constant. According to the latest measurements, the solar constant has a value of 136 mW/cm2 or 1.36 kW/m2 or 1.95 calories/cm2 per minute.