The energy of electron in an excited hydrogen atom is `-3.4eV`. Its angular momentum according to bohr's theory will be

Options

A. `3.72 xx 10^(-34) Js`
B. `2.10 xx 10^(-34) Js`
C. `1.51 xx 10^(-34)Js`
D. `4.20 xx 10^(-34) Js`

Answer

B

Explanation

`e=- 3.4 eV and r= ( kze^2 )/( 2E) `
angular momentum = mvr
`implies 1/2 mv^2 =E = 3.4 xx (10 ^(-19) xx 1.6)`
`implies m^@ v^2 = (9.1 xx 10^(-31) ) 2 xx 3.4 xx 1.6 xx 10^(-19) = 99.008 xx 10 ^(-50)`
`mv = 9.95028 xx 10^(25)`
` therefore L = ( 9.95028 xx 10^(25))((9 xx 10^9 xx 1 xx ( 1.6 xx 10^(-19))^2)/(2xx (3.4 )))`
`= 2.10 xx 10^(-34)`Js.