Question

Mesons are found in

• A. Alpha rays
• B. Laser beam
• C. X-rays
• D. Cosmic rays

Hint:

Recall that mesons are massive particles created in high energy collisions, not photons like laser or X-ray light.

Answer 1

The Correct Option is D

Separate the four options into two simple groups, particles versus photons, and see which group mesons belong to.

1. Photons carry electromagnetic energy but have no rest mass. Laser beams and X-rays are both made purely of photons, just of different wavelengths, so neither can contain mesons, which are massive particles.
2. Alpha particles are helium nuclei, two protons and two neutrons bound together, emitted from unstable heavy nuclei during radioactive decay. They are a completely different kind of particle from mesons.
3. Cosmic rays, on the other hand, are a stream of very energetic particles from space. When they hit the atmosphere, the huge collision energy is enough to create new particles out of pure energy, following Einstein's mass energy relation. Among the particles created in these collisions are pions, which are mesons.

Since mesons need a high energy particle collision to be produced, and cosmic ray impacts on the atmosphere provide exactly that, cosmic rays are the environment where mesons are actually found.