#### Question

What is the wavelength of a beam of neutron having:

⦁ An energy of 0.025 eV?

⦁ 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.

#### Solution

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)`

=1.8095A°.

Hence wavelength is equal to=1.8095A°.

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 = 5.721 × 10 ^{-11} joules.

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