An eletromagnetic wave of frequency 28 MHz passes through the lower atmosphere of earth and gets incident on the ionosphere.Shall the ionosphere reflects these waves?

Electromagnetic waves of frequency ……. are reflected from ionosphere.

The highest frequency of radio waves which the when sent at some angle towards the ionosphere , gets reflected from ionosphere and returns to earth is called ……. .

The highest frequency of radio waves which the when sent at some angle towards the ionosphere , gets reflected from ionosphere and returns to earth is called ……. .

Electromagnetic waves of frequencies higher than 9sqrt(2) MHz are found to be not reflected by the ionosphere on a particular day at a place. The maximum electron density in the ionosphere is :

Electromagnetic waves of frequencies higher than 9sqrt(2) MHz are found to be not reflected by the ionosphere on a particular day at a place. The maximum electron density in the ionosphere is :