An X-ray tube operates on $30\: kV$. The minimum wavelength emitted is :

Question

$\begin {array} {1 1} (a)\;6.6\: A^{\circ} & \quad (b)\;1.2\: A^{\circ} \\ (c)\;0.133\: A^{\circ} & \quad (d)\;0.4\: A^{\circ} \end {array}$