Electrons of mass m with de-Broglie wavelength ``\lambda``
fall on the target in an X-ray tube. The cutoff
wavelength (``\lambda_0``) of the emitted X-ray is :-
(1)``\lambda_0``= ``\frac {2m^2c^2\lambda^3}{h^2}``
(2) ``\lambda_0``= ``\lambda``
(3)``\lambda_0``= ``\frac {2mc\lambda^2}{h}``
(4) ``\lambda_0``= ``\frac {2h}{mc}``