If λe, λp and λα, be the de-Broglie wavelength of electron, proton an…

Considering that the question indicates if the particles have same speed or K.E or accelerating potential. (Although not mentioned in question)

λ = \(\frac{h}{mv}\) or λ = \(\frac{h}{\sqrt{2m(KE)}}\) or λ = \(\frac{h}{\sqrt{2mqV}}\)

In all of the above possibilities

 λ ∝ \(\frac{1}{\sqrt{mq}}\)

And   m_p = 1836 m_e ,  m_α = 4m_p 

\( \sqrt{(m q)_e} < \sqrt{(m q)_p} < \sqrt{(m q)_\alpha} \)

∴ From the above relation 

λ_α < λ_p < λ_e