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What is the de Broglie wavelength of a neutron in thermal equilibrium at temperature T?

1. 30.8 / √T Å
2. 3.08 / √T Å
3. 0.308 / √T Å
4. 0.0308 / √T Å

Correct answer: 30.8 / √T Å

Solution

For a thermal neutron with kinetic energy ~kT, p = sqrt(2*m*k*T) and lambda = h/p = h/sqrt(2*m*k*T) ~ 30.8/sqrt(T) Angstrom.

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