High-energy rays (like X-rays) The Electromagnetic Spectrum shows the different forms of electromagnetic radiation, with cosmic and gamma rays having the highest frequency and the highest energy, making them potentially the most dangerous to humans. When a radioactive sample decays, it emits particles. The rate of the radioactive decay does not vary by just changing temperature, pressure, or any other factors. Hence, a radioactive sample continues to decay. When much amount of the radioactive particle is present, the activity is higher & vice versa.