Electrons with de-Broglie wave length $$\lambda$$ fall on the target in an X-ray tube. The cut-off wavelength of the emitted X-rays is

A

$$\lambda_0 = \frac{2mc \lambda^2}{h}$$

B

$$\lambda_0 = \frac{2h}{mc}$$

C

$$\lambda_0 = \frac{2 m^2 c^2 \lambda^3}{h^2}$$

D

$$\lambda_0 = \lambda$$