A non-relativistic particle of fixed mass has de Broglie wavelength λ. Its speed is increased until its wavelength becomes 0.90λ. By what percentage has the speed increased?
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Question

A non-relativistic particle of fixed mass has de Broglie wavelength λ. Its speed is increased until its wavelength becomes 0.90λ. By what percentage has the speed increased?

G1 Physics · Accepted Answer

For fixed mass, λ = h ÷ (mv), so λ is inversely proportional to v. Therefore, v₂ ÷ v₁ = λ₁ ÷ λ₂ = 1 ÷ 0.90 ≈ 1.111. Thus the speed increases by approximately (1.111−1)×100 ≈ 11.1%. Correct option: C.