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 radiotelescopes 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?

(b)

Yes, long distance TV transmission requires UHF and still higher frequencies. Ionosphere does not reflect frequencies more than 30 MHz and hence satellites are used to reflect these waves.

(c)

With reference to X-rays astronomy, X-rays are absorbed by the atmosphere. But visible and radio waves can penetrate it. Thus, optical and radio telescopes are built on the ground, while X-rays astronomy is possible only with help of the satellites orbiting the earth.

(d)

It absorbs ultraviolet radiations from the sun and prevents it from reaching the earth's surface and causing damage to life.

(e)

The temperature of the earth would be lower because of  the absence of  Greenhouse effect,which retains the heat from sun in the atmosphere.

(f)

The clouds produced by global nuclear war would perhaps cover substantial parts of the sky preventing solar light from reaching many parts of the globe. This would cause a winter.