Question

Statement A: At great heights from the surface of earth , ionisation of air molecules is low
Statement B: Electromagnetic waves of frequencies beyond 30 MHz penetrate ionosphere and escape

• A. both A and B are correct
• B. both A and B are wrong
• C. only A is correct
• D. only B is correct

Answer 1

The correct option is A both A and B are correct

High solar activity can generate hard X-rays (wavelength < 1 nm) that ionize N₂ and O₂. Recombination rates are high in the D layer, so there are many more neutral air molecules than ions. Thus, at large heights ionization of air molecules is low. As the frequency increases, the penetration ability increases. Some of the high frequency waves are not able to penetrate the atmosphere but all SHF waves can penetrate. these waves are all above 30 MHz.