# What is the de Broglie wavelength of a dust particle of mass $1 \times 10^{-9}$ kg drifting with a speed of $\;2.2 m/s$

$\begin {array} {1 1} (a)\;0.3 \times 10^{-25}m & \quad (b)\;3 \times 10^{-28}m \\ (c)\;3 \times 10^{-25}m & \quad (d)\;30 \times 10^{-25}m \end {array}$

Ans : (c) $3 \times 10^{-25}m$
$m = 10^{-9}kg\: \: \: \: \: \: \: v=2.2 m/s$
$\lambda = h/mv$
$= (6.6 \times 10^{-34} )/ (2.2 \times 10^{-9} ) = 3 \times 10^{-25} m$

edited Mar 13, 2014