The de-Broglie wavelength of neutrons in thermal equilibrium at temperature T is

de Broglie wavelength of neutronsin thermalequilibrium at temperature T isλ=h2mkBTwhere $m$ is the mass of the neutron kB is the Boltzmann constant h is the Planck's constant Here, m=1.67×10-27 kg kB=1.38×10-23 J K-1 h=6.63×10-34 J s ∴  λ=6.63×10-342×1.67×10-27×1.38×10-23×T           =3.08×10-34×1025T m            =30.8×10-10T=30.8TAo