Question

In the decay ⁶⁴Cu → ⁶⁴Ni + e⁺ + v, the maximum kinetic energy carried by the positron is found to be 0.650 MeV.
(a) What is the energy of the neutrino which was emitted together with a positron of kinetic energy 0.150 MeV?
(b) What is the momentum of this neutrino in kg m s⁻¹?
Use the formula applicable to a photon.

Answer 1

Given:
Maximum kinetic energy of the positron, K = 0.650 MeV

(a) Neutrino and positron are emitted simultaneously.
∴ Energy of neutrino = 0.650 − Kinetic energy of the given positron

 = 0.650 − 0.150
 = 0.5 MeV = 500 keV

(b) Momentum of the neutrino, `P = E/c`

Here, E = Energy of neutrino
  c = Speed of light

⇒ `P = (500 xx 1.6 xx 10^-19)/(3 xx 10^8) xx 10^3`

= `2.67 xx 10^-22  "Kgms"^-1`