The speed of an electron having a wavelength of `10^(-10) m` is

Options

A. `4.24 xx 10^(6) m//s`
B. `5.25 xx 10^(6) m//s`
C. `7.25 xx 10^(6) m//s`
D. `6.25 xx 10^(6) m//s`

Answer

C

Explanation

The de - Broglie wavelength is given by `lambda = (h)/(p)`
where `h` is planck's constant and `p` is momentum.
Also `p = mu`
where `m` is mass , `u` is velocity , `u = (h)/(m lambda)`
putting the numerical values , we have
`h = 6.6 xx 10^(-34) Js , m = 9.1 xx 10^(-31) kg`,
`lambda = 10^(-10) m`
`rArr u = (6.6 xx 10^(-34))/(9.1 xx 10^(-31) xx 10^(-10)) = 7.25 xx 10^(6) m//s`