What is the
de-Broglie wavelength of an electron with kinetic energy of 120 eV?

Explanation

K.E. of electron =E=120 eV
`E=120 xx 1.6 xx 10^(-19)J`
Mass of electron `=m = 9.1 xx 10^(-31)kg`
de-Broglie wavelength of electron `=lamda= (h)/(sqrt(2mE))`
`lamda= (6.62 xx 10^(-34))/(sqrt(2 xx 9.1 xx 10^(-31) xx 120 xx 1.6 xx 10^(-19)))`
`lamda= (6.62 xx 10^(-34))/(59.11 xx 10^(-25))`
`lamda= 0.1120 xx 10^(-9)m`
`lamda= 1.12 xx 10^(-10)m= 1.12 Å`
Momentum of electron `= P= (h)/(lamda)`
`P= (6.62 xx 10^(-34))/(1.12 xx 10^(-10))`
`P= 5.91 xx 10^(-24) kg m//s`