19
Question
Which of the following statement (s) are correct regarding the different layers of atmosphere:
Which of the following statement (s) are correct regarding the different layers of atmosphere:
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Solution
The correct options are
B D layer exists during day only
C layer F1 exists during day only and merges F2 at night
D layer F2 exists during both day and night
The D layer is the innermost layer, 60 km (37 mi) to 90 km (56 mi) above the surface of the Earth. Ionization here is due to Lyman series-alpha hydrogen radiation at a wavelength of 121.5 nanometre (nm) ionizing nitric oxide (NO). In addition, high solar activity can generate hard X-rays (wavelength < 1 nm) that ionize N2 and O2. Recombination rates are high in the D layer, so there are many more neutral air molecules than ions.This effect peaks around noon and is reduced at night due to a decrease in the D layer's thickness; only a small part remains due to cosmic rays. Hence it exists majorly during the day only.
E regions is a layer of ionised gas occurring between roughly 90–150 km (56–93 mi) above the ground — one of several layers in the Earth's atmophere. It reflects medium-frequency radio waves and because of this reflection, radio waves can be propagated beyond the horizon. It exits during both day and night, however, propagation is affected by time of day. During daytime, solar winds press it more towards the earth, limiting how far it can reflect radio waves.
The F region of the ionosphere is home to the F layer of ionization, also called the Appleton-Barnette layer. The F region contains ionized gases at a height of around 150–800 km above sea level, placing it in the Earth’s thermosphere, a hot region in the upper atmosphere, and also in the heterospher, where chemical composition varies with height. The F-region is located directly above the E region. The F1 layer is the lower sector of the F layer and exists from about 150 to 220 km above the surface of the Earth and only during daylight hours. It is composed of a mixture of molecular ions O2+ and NO+, and atomic ions O+. The F2 layer exists from about 220 to 800 km above the surface of the Earth. The F2 layer is the principal reflecting layer for HF communications during both day and night.
B D layer exists during day only
C layer F1 exists during day only and merges F2 at night
D layer F2 exists during both day and night
The D layer is the innermost layer, 60 km (37 mi) to 90 km (56 mi) above the surface of the Earth. Ionization here is due to Lyman series-alpha hydrogen radiation at a wavelength of 121.5 nanometre (nm) ionizing nitric oxide (NO). In addition, high solar activity can generate hard X-rays (wavelength < 1 nm) that ionize N2 and O2. Recombination rates are high in the D layer, so there are many more neutral air molecules than ions.This effect peaks around noon and is reduced at night due to a decrease in the D layer's thickness; only a small part remains due to cosmic rays. Hence it exists majorly during the day only.
E regions is a layer of ionised gas occurring between roughly 90–150 km (56–93 mi) above the ground — one of several layers in the Earth's atmophere. It reflects medium-frequency radio waves and because of this reflection, radio waves can be propagated beyond the horizon. It exits during both day and night, however, propagation is affected by time of day. During daytime, solar winds press it more towards the earth, limiting how far it can reflect radio waves.
The F region of the ionosphere is home to the F layer of ionization, also called the Appleton-Barnette layer. The F region contains ionized gases at a height of around 150–800 km above sea level, placing it in the Earth’s thermosphere, a hot region in the upper atmosphere, and also in the heterospher, where chemical composition varies with height. The F-region is located directly above the E region. The F1 layer is the lower sector of the F layer and exists from about 150 to 220 km above the surface of the Earth and only during daylight hours. It is composed of a mixture of molecular ions O2+ and NO+, and atomic ions O+. The F2 layer exists from about 220 to 800 km above the surface of the Earth. The F2 layer is the principal reflecting layer for HF communications during both day and night.
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