1) An energy of 0.025 eV?

2) An electron and photon each have wavelength of 2A°. what are their momentum and energy ?

$m_n=1.676×10^{(-27)}kg, h=6.625×10^{(-34)}J-sec. $

Given Data :- energy of neutron = 0.025eV.

To find :- wavelength of a beam.

Calculation :- λ = h/(√2meV)

= $ (6.626×10^{(-34)})/(√2×1.676×10^{(-27)}×0.025×10^{(-19)}×1.6)$

= 1.8095 A°.

Hence wavelength is equal to = 1.8095 A°.

2.Given Data :- λ=2A° , $m_n=1.676×10^{(-27)}kg, h=6.625×10^{(-34)}J-sec.$

To find :- momentum and energy.

Calculations :- λ = h/p , ………………….(for momentum)

$2×10^{(-10)} = (6.625×10^{(-34)})/p$

P = 3.3125 ×10^{(-24)}kg-m/sec.

λ = h/(√2mE)

$2×10^{(-10)} = ( 6.625×10^{(-34)})/(√2×1.676×10^{(-27)}×E)$

E = $5.721 ×10^{(-11)} joules.$

Hence momentum = $3.3125 ×10^{(-24)}kg-m/sec$. and energy is = $5.721 ×10^{(-11)}$ joules.