A proton and an alpha particle have the same de Broglie wavelength. What is the ratio of their velocities? (mₚ = 1.67 ×
mₚ vₚ = m_α v_α. vₚ/v_α = m_α/mₚ ≈ 4.
Ref: NCERT Class 11 Chemistry > Chapter 2: Structure of Atom > Topic: Quantum Mechanical Model - de Broglie Heisenberg and Schrodinger