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 :

Options

A. `sqrt(5)xx10^(12)m^(-3)`
B. `sqrt(2)xx10^(12)m^(-3)`
C. `2xx10^(12)m^(-3)`
D. `5xx10^(12)m^(-3)`

Explanation

Here, `v_(c)=9(N_("max"))^(1//2)`
or `N_("max")=((v_(c))/(9))^(2)=(v_(c)^(2))/(81)=((10xx10^(6))^(2))/(81)`
`=1.3xx10^(12)m^(-3)`