A. For what kinetic energy of neutron will the associated de Broglie wavelength be `1.40xx10^(-10)m`?
B. Also, find the de Broglie wavelength of a neutron, in thermal equilibrium with matter, having an average kinetic energy of `((3)/(2))` kT at `300 K`. Given the mass of neutron`=1:66xx10^(-27)kg` and `k=1.38xx10^(-23)Jkg^(-1)`.`

Explanation

To solve the given problem, we will break it down into two parts as specified in the question.

### Part A: Finding the Kinetic Energy of the Neutron

1. **Given Data**:
- De Broglie wavelength, \( \lambda = 1.40 \times 10^{-10} \, \text{m} \)
- Mass of neutron, \( m_n = 1.66 \times 10^{-27} \, \text{kg} \)
- Planck's constant, \( h = 6.63 \times 10^{-34} \, \text{Js} \)
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