Answer the following questions :
(a) Optical and radio telescopes are built on the ground while X-ray astronomy is possible only from satellites orbiting the Earth. Why ?
(b) The small ozone layer on top of the stratosphere is crucial for human survival. Why ?

Explanation

(a) Since, the transmission of signals using ground waves restricted upto a frequency of 1500 Hz to save the loss of energy.
(b) The ultraviolet radiations from the sun is harmful to the living cells and plants. The ozone layer absorbs ultraviolet radiation and prevents it from reaching the earth. It also keeps the earth warm by trapping infra-red radiations.