Question

Assertion: Television signals are recieved throgh sky-wave propagation.
Reason: The ionosphere reflects em wave of frequencies greater than a critical frequency.
A. If both the assertion and reason are true and reason is a true explantion of the assertion.
B. If both the assertion and reason are true but the reason is not true the correct explantion of the assertion.
C. If the assertion is true but reason false
D. If both the assertion and reason are false.

Answer 1

Correct Answer - D
In sky-wave propagation the radio waves which have frequency between `2 MHz` to `3MHz`, are reflected back to the ground by the ionosphere. But radio waves having frequency greater than `30 MHz` cannot be reflected by the ionosphere because at this frequency they penetrate the ionosphere. It makes the sky-wave propagation less reliable for propagation of `TV` signal having frequency greater than `30 MHz`. Critcal frequency is defined as the highest frequency that is returened to the earth by the ionosphere. Thus, above this frequency a wave whether it is electronagnetic will penetrate the ionosphere and is not reflected by it.