A thermal neutron (mass 1.675x10^-27 kg) has kinetic energy 0.040 eV. Use h = 6.626x10^-34 J s and 1 eV = 1.6x10^-19 J. Find its de Broglie wavelength in AA, to two decimals.

JEE Main levelNumerical answerDifficulty 2 of 3as128

A thermal neutron (mass $1.675 \times 1 0^{- 27} kg$ ) has kinetic energy $0.040 eV$ . Use $h = 6.626 \times 1 0^{- 34} J s$ and $1 eV = 1.6 \times 1 0^{- 19} J$ . Find its de Broglie wavelength in $\overset{˚}{A}$ , to two decimals.

Numerical answer type, answer in Angstrom, tolerance 0.01.

K = 0.040 \times 1.6 \times 1 0^{- 19} = 6.40 \times 1 0^{- 21} J

λ = h / 2 m K = 1.431 \overset{˚}{A}