Annihilation

When matter and its antimatter (or particles and their corresponding antiparticles) collide, they can annihilate each other. That means they destroy each other and produce energy in the form of photons, otherwise known as electromagnetic waves.

Annihilation converts the mass of the matter and antimatter into energy.

Direction of photon propagation

After annihilation, the photons produced are emitted in opposite directions, perpendicular to the original direction of the particles. This is because of the conservation of momentum - the momentum before the annihilation must equal the momentum after the annihilation, and the momentum before was 0.

Energy of the photons

The energy of the photons produced from the annihilation can be calculated using the equation:

E = mc^2