ASNT Radiographic Testing Practice Test 2026 – Comprehensive All-in-One Guide for Exam Success!

The radiation intensity of a radioisotope decreases with time due to the process of radioactive decay. Radioactive materials emit radiation as they transform into more stable isotopes, and this decay occurs at a characteristic rate known as the half-life.

As time progresses, the quantity of the radioactive material diminishes, leading to a corresponding decrease in radiation intensity. The half-life is crucial because it defines the time required for half of the radioactive atoms in a sample to decay. Thus, after a number of half-lives, the amount of remaining radioactive material—and, consequently, the radiation it emits—will have significantly reduced.

The other options suggest different behaviors of radiation intensity that are not consistent with the principles of radioactive decay. Radiation from a radioisotope does not increase or remain constant; it also does not fluctuate unpredictably. Understanding this decay process is fundamental in fields like radiographic testing, where consistent and predictable radiation levels are essential for accurate measurements and safety.