Question

If particles are moving with same velocity, then which has maximum de Broglie wavelength?

• A. proton
• B. $\alpha$- particle
• C. neutron
• D. $\beta$ - particle

Answer 1

Answer: (D)

de Broglie wavelength for a particle is given by $\lambda =\frac{h}{p}=\frac{h}{mv}$, where $m,v$ and $p$ are the mass, velocity and momentum respectively. $h$ is Planck's constant. Now, since all the particles are moving with same velocity, the particle with least mass will have maximum de-Broglie wavelength. Out of the given four particles (proton, $\alpha$-particles, i.e. He nucleus and $\beta$-particles, i.e. electrons) $\beta$-particles has the lowest mass and therefore it has maximum wavelength.