Assertion : Television signals are received through sky-wave...

In sky wave propagation, the radio waves having frequency range $2 \mathrm{MHz}$ to $30 \mathrm{MHz}$ are reflected back by the ionosphere. Radio waves having frequency nearly greater than $30 \mathrm{MHz}$ penetrates the ionosphere and is not reflected back by the ionosphere. The TV signal having frequency greater than $30 \mathrm{MHz}$ therefore cannot be propagated through sky wave propagation. In case of sky wave propagation, critical frequency is defined as the highest frequency that 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 is not reflected by it.