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An electron, an α-particle and a proton have the same kinetic energy. Which of these particles has the shortest de Broglie wavelength?

Asked in GUJCET 2022 · Same or changed energy

Answer: (1) α-particle

Step-by-step solution

Given: the same kinetic energy K for all three particles.

Idea: p = √2mK, so λ = h/(√2mK) ∝ 1/(√m) at fixed K.

The heaviest particle has the largest momentum and so the shortest wavelength.

Masses: mₑ < mₚ < m_α, with m_α ≈ 4mₚ.

So the α-particle has the shortest de Broglie wavelength.

Why the other options are wrong

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