Electromagnetic waves of frequencies higher than `9 sqrt2 MHz` are found to be reflected by the ionosphere on a particular day at a place. The maximum electron density in the ionosphere is

Options

A. `sqrt5 times 10^12 m^-3`
B. `sqrt2 times 10^12 m^-3`
C. `2 times 10^12 m^-3`
D. `5 times 10^12 m^-3`

Answer

C

Explanation

The frequency of electromagnetic waves
`v=9sqrt("maxim um el ectron density")`
or `v=9sqrt(d_(max))`
or `9sqrt2 times 10^6 =9sqrt(d_(max))`
or `sqrt2 times 10^6=sqrt(d_(max))`
or `d_(max)=2 times 10^12 m^-3`