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Answer the following : (a) Name the em...

Answer the following :
(a) Name the em waves which are suitable for radar system used in aircraft navigation. Write the range of frequencey of these waves.
(b) If the earth did not have atmosphere, would its average surface temperature be higher or lower than what it is now? Explain

Text Solution

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(a) Microwaves are suitable for radar systems used in aircraft navigation. The range of frequency for these waves is 109Hz to 1012Hz.
(b) In the absence of atmosphere, there would be no greenhouse effect on the surface of the Earth. As a result, the temperature of the Earth would decrease rapidly, making it difficult for human survival.
(c) An em wave carries a linear momentum with it. The linear momentum carried by a protion of wave having energy U is given by p = Uc.
Thus, if the wave incident on a material surface is completely absorbed, it delivers energy U and momentum p = Uc to the surface.
If the wave is totally reflected, the momentum delivered is p = 2Uc because the momentum of the wave changes from p to -p . Therefore, if follows that an em waves incident on a surface exert a force and hence a pressure on the surface.
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A : If the earth did not have an atmosphere, its average surface temperature would have been lower. R : In the absence of atmosphere, the green house effect will be absent.

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Knowledge Check

  • Assertion : If earth did not have atmosphere, its average surface temperature would be lower than what it is now Reason : Green house effect of the atmosphere would be absent, if earth did not have atomosphere.

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    C
    If assertion is true but reason is false
    D
    If both assertion and reason are false

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