A particle which has zero rest mass and non-zero energy and momentum must travel with a speed
Step 1. Given data:
Rest mass 0
Let speed of the particle;
speed of light;
mass of the particle when it is moving
Step 2. Formula used:
As we know that the mass of a moving particle is given by the following formula,
, where all the variables are described above.
Step 3. Explanation:
Since it is given that the rest mass of the particle is zero, so . Putting the value of in equation, we get
, squaring both sides, we get
It shows that the speed of the particle is equal to the speed of light.
Particle is a photon and it travels with a velocity equal to light in vacuum.
Hence, a particle that has zero rest mass and non-zero energy and momentum must travel with a speed equal to the speed of light.