Question
A proton and an a particle are accelerated through the same potential difference. Which one of the two has (i) greater de-Broglie wavelength, and (ii) less kinetic energy? Justify your answer.

Answer

  1. $\lambda =\frac{\text{h}}{\text{p}} =\frac{\text{h}}{\sqrt{2\text{mqV}}}$

$\because(\text{mq}) \text{is more for }\alpha - \text{particle} , \text{we have}$

$\lambda_{proton} > \lambda_{\propto} - particle$

(Also, $\frac{\lambda_{proton}}{\lambda_{\alpha}} =2\sqrt{2}(\text{ or }\sqrt{8} ) $

  1. K.E. = q V

$\because $q is less for proton, we have

$(\text{K.}\text{E} )_{proton} < (\text{K.}\text{E} )_{\alpha - particle}$

$\text{Also},\frac{(\text{K.E.})\propto}{(\text{K.E.})_{\rho}} = 2 ) $.

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