Find the force exerted on a particle by a uniform field if the concentrations of these particles at two levels separated by the distance `Delta h = 30 cm` (along the field) differ by `eta = 2.0` times. The temperature of the system is equal to `T = 280 K`.

Explanation

If the force exerted is `F` then the law of variation of concentration with height reads
`n(Ƶ) = n_0 e^(- F Ƶ//kT)` So, `eta = e^(F Delta h//kT)` or `F = (kT 1n eta)/(Delta h) = 9 xx 10^-20 N`.