Suppose that a particle at rest with mass m decays into a photon and another particle with mass m/2 , which recoilds in a direction opposite to the photon. Using the conservation of energy and momentum find the momentum of the recoiling particle

Explanation:

To find the momentum of the recoiling particle you can use the momentum formula for a photon:

before the decay the momentum is zero. Hence, after the decay the momentum of the photon plus the momentum of the recoiling particle must be zero:

where pr is the momentum of the recoiling particle.

no

sodium is solid at rt