Atmospheric Refraction : You know that the earth is surrounded by a layer of air called the atmosphere. The density of air in the atmosphere is not the same everywhere. In general, it is greatest at the earth's surface and goes on decreasing as we move higher. The refractive index of air depends on its density-higher the density of air, greater its refractive index. Under standard conditions of temperature, humidity, etc., near the earth's surface, the refractive index of air is slightly greater than 1. It decreases with height, and is very close to 1 in the outermost region of the atmosphere. The changes in refractive index of air give rise to many phenomena. For example, a rising current of hot air makes the objects viewed through it seem to flicker. You might have seen this happen as hot air rises above the heated surface of roads on hot summer days or above a large burning stove or chulha.
Hot air has less density, and hence, less refractive index than normal or cold air. At a point in the area above a hot surface, the refractive index keeps on changing as currents of hot air passes through it. So, the amount by which light passing through it is bent keeps on changing. This makes the objects viewed through this area seem to sway or flicker.
Which of the following statement are not correct for Atmospheric refraction 1. A rising current of hot air makes the objects viewed through it seem to flicker because of atmospheric refraction. 2. Under standard conditions of temperature, humidity, etc., near the earth's surface, the refractive index of air is slightly greater than 1. 3. It decreases with height, and is very close to 1 in the outermost region of the atmosphere. | |||
Right Option : D | |||
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Under standard conditions of temperature, humidity, etc., near the earth's surface, the refractive index of air is _________________. | |||
Right Option : A | |||
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Arrange the following in the increasing order of density. Hot air, Normal air, Cold air | |||
Right Option : A | |||
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