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the olyeerverie eyr the eky through 11.5 ATMOSPHERIC REFRACTION Yout mikht have observed the apparent random wo swderthg of objects seen through a turbulent stream of hiot, wove a fire or a radiator. The air just above the fire becomes her he hir is lighter (less dense) than above in and has a refractive index sitions of the refracting medium the the to atarionary, the apparent position of the object, as seen through air fuctuates. This wavering is thus an effect of atmospheric refes (irfraction of light by the earth's atmosphere) on a small scale ing focal emironment. The twinkling of stars is a similar Twinkling of stars The twinkling of a star is due to atmospheric refraction. starlight. The starlight, on entering the earth's atmospone undergoes refraction continuously before it reaches the end The atmospheric refraction occurs in a medium of graduey changing refractive index. Since the atmosphere beess starlight towards the normal, the apparent position of star is slightly different from its actual position. The se appears slightly higher (above) than its actual position wing viewed near the horizon (Fig. 11.9). Further, this apparici position of the star is not stationary, but keeps on changy. slightly, since the physical conditions of the eartix atmosphere are not stationary, as was the case in previous paragraph. Since the stars are very distant, thing of fight coming point-sized sources of light. As the path ofrepp of light coming from the star goes on varying slightly, tin apparent position of the star fluctuates and the amountol Science

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Updated on: Jul 28, 2022