Final answer:
Ultraviolet (UV) light is most commonly used for killing bacterial cells because it causes mutations in DNA, leading to cell death without penetrating surfaces.
Step-by-step explanation:
The type of electromagnetic radiation most commonly used to kill bacterial cells is ultraviolet (UV) light. This form of nonionizing radiation is less energetically intense compared to ionizing forms such as X-rays and gamma rays. Unlike its more penetrative counterparts, UV light does not penetrate cells or their packaging, which makes it safe for various applications. Still, the mechanics of its efficacy are profound.
When UV light is shone onto bacterial DNA, it induces the formation of thymine dimers, which can cause mutations in the DNA when the cells try to replicate, leading to cell death. Therefore, UV light is widely incorporated into water purification systems, used in surgical suites, and is portable for campers to purify water.