Height h(400=m) from the ground at place A, from which the readiowaves can be transmitted. There is a receive at station B on earth at a distance d(=125km), which can receive the signal from station A. The radiowaves can reach the station B, either through earth's atmosphere or through satellite. There are four main layers in earth's atmosphere named D,E,`F_(1)` and `F_(2)` which play effective role in radio communication. The electron density of these layers is `4xx10^(8), 2xx10^(11),5xx10^(11)` and `8xx10^(11)m^(-3)`. The radius of the earth is `6.4xx10^(6)m`.
On a particular day, the maximum frequency reflected from the ionosphere is 9 MHz. On another day, it was found to increase by 1 MHz. The ratio of maximum electrom density of the ionosphere on the two days is

Options

A. `9//8`
B. `3//2 sqrt(2)`
C. `100/81`
D. none of the above

Explanation

`(N'_("max"))/(N_("max"))=((v'_(C))/(v_(C)))^(2)=((8_1)/(8))^(2)=(81)/(64)`