Answer the following questions:
$(a)$ Long distance radio broadcasts use short-wave bands. Why?
$(b)$ It is necessary to use satellites for long distance $TV$ transmission. Why?
$(c)$ Optical and radio telescopes are built on the ground but $X$-ray astronomy is possible only from satellites orbiting the earth. Why?
$(d)$ The small ozone layer on top of the stratosphere is crucial for human survival. Why?
$(e)$ If the earth did not have an atmosphere,would its average surface temperature be higher or lower than what it is now?
$(f)$ Some scientists have predicted that a global nuclear war on the earth would be followed by a severe 'nuclear winter' with a devastating effect on life on earth. What might be the basis of this prediction?

(N/A) Long distance radio broadcasts use short-wave bands because these waves are refracted by the ionosphere,allowing them to travel long distances around the curvature of the Earth.
$(b)$ $TV$ signals have very high frequencies and high energies. They are not reflected by the ionosphere; therefore,satellites are required to receive and retransmit these signals for long-distance communication.
$(c)$ The Earth's atmosphere absorbs $X$-rays,preventing them from reaching the ground. However,visible light and radio waves can penetrate the atmosphere,allowing optical and radio telescopes to operate on the ground.
$(d)$ The ozone layer absorbs harmful ultraviolet $(UV)$ radiation from the Sun,which would otherwise cause severe damage to living organisms,including skin cancer and genetic mutations.
$(e)$ Without an atmosphere,there would be no greenhouse effect. The Earth's average surface temperature would be significantly lower than it is now because the atmosphere traps heat radiated from the surface.
$(f)$ $A$ global nuclear war would release massive amounts of smoke and dust into the atmosphere. These particles would block sunlight from reaching the Earth's surface,leading to a drastic drop in temperature,known as a 'nuclear winter',and the depletion of the ozone layer.