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Which of the following has the longest de Broglie wavelength if they are moving with the same velocity?

Asked in GUJCET 2007 · Equal wavelengths and equal speeds

Answer: (4) β-particle

Step-by-step solution

Given: all four move with the same velocity v.

Idea: λ = h/(mv), so at equal v the wavelength is inversely proportional to the mass.

A β-particle is a fast electron, mass 9.1×10⁻³¹ kg, the lightest of the four.

The proton and neutron are about 1836 and 1839 times heavier than it, and the α-particle about 7300 times.

So the β-particle has the longest de Broglie wavelength.

Why the other options are wrong

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