Frequencies higher than 10 Mhz are found not to be reflected by the ionosphere on a particular day at a place. Calculate the maximum electron density of the ionosphere.

Frequencies higher than 5 MHz are found not to be reflected by the ionosphere on a particular day at a place. The maximum electron density of the ionosphere is

Frequecies higher than 5 MHz are found not to be reflceted by the ionosphere on a particular day at a place. The maximum electron density of 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 :

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 :

How is the critical frequency related to maximum electron density in the ionosphere?