Ultraviolet Radiation

As highlighted in NCERT Class 12, Chapter 8 (Electromagnetic Waves), ultraviolet radiation lies just beyond the violet end of the visible spectrum, with wavelengths shorter than about 400 nm and correspondingly high photon energies. These energetic photons can damage biological molecules such as DNA, causing sunburn and increasing cancer risk. Fortunately, the ozone layer in the upper atmosphere absorbs most of the harmful ultraviolet from sunlight, shielding life on the surface. Infrared radiation is lower in energy and is felt as heat rather than absorbed by ozone in this protective way. Radio waves have extremely low photon energy and pass through the atmosphere freely without significant biological harm. Visible light is essential for vision and photosynthesis and is not the radiation blocked by ozone for protective reasons. A plausibility check based on photon energy confirms that only ultraviolet carries enough energy to threaten biological molecules while still being efficiently absorbed by atmospheric ozone, so ultraviolet radiation is the correct answer.