Question

Assertion :Television signals are received through sky wave propagation. Reason: The ionosphere reflects electromagnetic waves of frequencies greater than a certain critical frequency.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Assertion is incorrect but Reason is correct

Answer 1

The correct option is D Assertion is incorrect but Reason is correct

In sky wave propagation, the radio waves having frequency range $2MHz$ to $30MHz$ are reflected back by the ionosphere. Radio waves having frequency nearly greater than $30MHz$ penetrates the ionosphere and is not reflected back by the ionosphere. The TV signals have frequencies greater than $30MHz$, therefore cannot be propagated through sky wave propagation. In case of sky wave propagation, critical frequency is defined as the highest frequency is returned to the earth by the considered layer of the ionosphere after having sent straight to it. Above this frequency, a wave will penetrate the ionosphere and not be reflected by it.