Energy of an electron is given by `E = - 2.178 xx 10^-18 J ((Z^2)/(n^2))`. Wavelength of light required to excited an electron in an hydrogen atom from level `n = 1` to `n = 2` will be
`(h = 6.62 xx 10^-34 Js` and `c = 3.0 xx 10^8 ms^-1`).

Options

A. `8.500 xx 10^(-7) m`
B. `1.214 xx 10^(-7) m`
C. `2.816 xx 10^(-7) m`
D. `6.500 xx 10^(-7) m`

Answer

B

Explanation

`Delta E = (hc)/(lamda) = 2.178 xx 10^(-18) ((1)/(1^(2)) - (1)/(2^(2))) Z^(2)`
`= 2.178 xx 10^(-18) xx (3)/(4) xx 1 (Z = 1 " for " H)`
or `lamda = (hc)/(Delta E) = ((6.62 xx 10^(-34)) (3 xx 10^(8)) xx 4)/(2.178 xx 10^(-18) xx 3)`
`= 1.214 xx 10^(-7) m`