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The use of nuclear weapons would cause the formation of smoke clouds preventing the light from the sun reaching earth surface and it will also deplete the atmosphere and therefore stopping the greenhouse effect and thus doubling the cooling effect.
If the earth did not have an atmosphere its average surface temperature be lower than what it is now as in the absence of atmosphere there would be no greenhouse effect.
 The small ozone layer on top of the stratosphere is crucial for human survival as it absorbs the ultraviolet radiations coming from the sun which are very harmful to humans.
X-rays are absorbed by the atmosphere and therefore the source of X-rays must lie outside the atmosphere to carry out X-ray astronomy and therefore satellites orbiting the earth are necessary but radio waves and visible light can penetrate through the atmosphere and therefore optical and radio telescopes can be built on the ground.
As TV signals are of high frequencies they are not reflected by the ionosphere and therefore satellites are to be used to reflect them.
Long distance radio broadcasts use short-wave bands as these are refracted by the ionosphere.
EM wave one wavelength is taken from the range Temperature  Radio 100 cm Microwave 0.1cm 2.9 K Infra-red 100000ncm 2900K Light 50000 ncm 5800K Ultraviolet 100ncm X-rays 1 ncm Gamma rays 0.01 nm   These numbers indicate the temperature ranges required for obtaining radiations in different parts of the spectrum
Total power which is converted into visible radiation = 5% of 100W = 5W The above means 5J of energy is passing through the surface of a concentric sphere(with the bulb at its centre) per second. Intensity for a sphere of radius 10 m   =3.9810-3 Wm-2
Total power which is converted into visible radiation = 5% of 100W = 5W The above means 5J of energy is passing through the surface of a concentric sphere(with the bulb at its centre) per second. Intensity for a sphere of radius 1m   =0.398 Wm-2
As the electric field vector is directed along the negative x-direction and the electromagnetic wave propagates along the negative y-direction the magnetic field vector must be directed along the negative z-direction. () Therefore, 
From the given equation of the electric field, we can infer Electric field amplitude (E0) =3.1 NC-1   =1.0310-7 T
From the given equation of the electric field we can infer angular frequency() = 5.4108 rad s-1 Frequency() =  = =8.6107 Hz =86 MHz
The electric field vector is in the negative x-direction and the wave propagates in the negative y-direction.
The average energy density of the Electric field(UE)  =  =                 (as E=Bc) =                         =UB  Therefore the average energy density of the electric field is equal to the average energy density of the Magnetic field.
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