What maximum frequency from following which can be reflected from ionosphere -

What is the maximum frequency which can be transmitted by ground waves ?

On a particular day, the maximum frequency reflected from the ionosphere is 10 MHz The maximum electron density in ionosphere is

On a particular day, the maximum frequency reflected from the ionosphere is 10 MHz The maximum electron density in ionosphere is

Critical frequency that gets reflected back from ionosphere is

On a particular day, the maximum frequency reflected from the ionosphere is 12 MHz, On another day, it was found to decrease to 9 MHz. By what percentage the maximum electron density of the ionosphere has been decreased.

On a particular day, the maximum frequency reflected from the ionosphere is 10MHz. After 10 days, it increaesed to 11 MHz. What is the ratio of the maximum electron density of the ionosphere on these two days ?

On a particular day, the maximum frequency reflected from the ionosphere is 8 MHz. On other day it was found to increase to 9 MHz. Then ratio of maximum electron densities of the ionosphere on two days will be