Question

Assertion: Electromagnetic waves with frequencies smaller than the critical frequency of ionosphere cannot be used for communication using sky wave propagation.
Reason: The refractive index of the ionosphere becomes very high for frequencies higher than the critical frequency.

• A. S1 and S2 are true; S2 is a correct explanation of S1
• B. S1 and S2 are true; S2 is not a correct explanation of S1.
• C. S1 is true; S2 is false(d
• D. S1 is false; S2 is true.

Answer 1

The correct option is A S1 and S2 are true; S2 is a correct explanation of S1

Since, the waves would not be reflected from the ionosphere, so it cannot be used for communication.

so that correct option is A.