A beam of helium atoms moves with a velocity of `2.0 xx 10^3 ms^(-1)` . Find the wavelength of the particles constituting the beam. `(h = 6.626 xx 10^(-34)Js)`.

Explanation

Given, velocity of beam of helium atoms
`= 20 xx 10^(3) m "sec"^(-1)`
Mass of helium atom = `4/(6.022 xx 10^(23))`
`= 6.64 xx 10^(-24) g = 6.64 xx 10^(-27) kg`
According to de-Broglie equation, `lambda = h/(mv)`
`= (6.626 xx 10^(-34) kg m^2 s^(-1))/((6.64 xx 10^(-27)kg)xx(2.0 xx 10^3 ms^(-1)))`
`= 4.99 xx 10^(-11)m = 49.9 p m`.