Question

Which particle among the following will have the smallest de Broglie wavelength, assuming that they have the same velocity?

• A. Positron
• B. Photon
• C. $\alpha$ - particle
• D. Neutron

Answer 1

Answer: (C)

$\alpha$ - particle

The de Broglie equation is $\lambda =\frac{h}{p}=\frac{h}{mv}$
Here $h$ and $v$ are constant. So, $\lambda$ is inversely proportional to $m$.
Since the $\alpha$-particle has the highest mass among the given entities, it has the smallest de-Broglie wavelength.