Yes, nuclear bombs leave behind radiation, but the extent and duration depend on the type of detonation and circumstances. All nuclear weapons release intense radiation at the moment of explosion, including gamma rays and neutrons that can cause immediate harm over a wide radius. The primary concern for lingering radiation comes from radioactive fallout—particles of soil, debris, and vaporized bomb material that become contaminated with radioactive isotopes and fall back to Earth over hours to days. This fallout can spread hundreds of miles depending on wind patterns and can remain hazardous for years or decades. Surface or ground-level detonations produce significantly more fallout than high-altitude detonations. Additionally, some radioactive elements created during a nuclear explosion, like strontium-90 and cesium-137, have half-lives of 20-30 years, meaning they persist in the environment long after the explosion. Neutron activation of surrounding soil and structures can also create residual radioactivity. However, the radiation levels decrease over time as isotopes decay. Areas hit by nuclear weapons become contaminated enough that evacuation and long-term exclusion zones are typically necessary, though the severity varies greatly based on weapon yield, location, and environmental factors.