Radiation Safety Practice Exam

Which particle is known to be the fastest moving?

1. Alpha particle

2. Beta particle

3. Gamma ray

4. Neutron

The correct answer is: Gamma ray

The fastest moving particle among the options listed is the gamma ray. Gamma rays are a form of electromagnetic radiation, similar to X-rays, and they travel at the speed of light in a vacuum, which is approximately 299,792 kilometers per second (186,282 miles per second). This characteristic of gamma rays makes them significantly faster than the other particles mentioned. Alpha particles, which are composed of two protons and two neutrons, are relatively heavy and move at a much slower speed compared to gamma rays. Beta particles, which are high-energy, high-speed electrons or positrons emitted by certain types of radioactive decay, also travel at a speed that, while fast, is still less than that of gamma rays. Neutrons, although they have no charge and can penetrate materials well, do not move as quickly as gamma rays either; their speed depends on their energy but is not at the speed of light. Thus, understanding the nature of electromagnetic radiation and the properties of subatomic particles clarifies why gamma rays are recognized as the fastest among these particles.