Applications Of Em Spectrum

NCERT Class 12, Chapter 8 (Electromagnetic Waves) discusses the uses of different spectral regions based on their frequency and penetrating power. X-rays have very short wavelengths, roughly 0.01 to 10 nanometres, and high energy per photon, which lets them pass through low-density soft tissue while being strongly absorbed by dense bone and metal. This differential absorption produces the contrast seen in medical radiographs, making X-rays the standard tool for imaging fractures. Infrared radiation is absorbed by the skin and used for thermal imaging or heating, so it cannot penetrate to reveal bones. Microwaves are used in cooking and communication and are readily absorbed by water-containing tissue rather than passing through it. Radio waves have very low photon energy and pass through the body without producing useful contrast for imaging. A plausibility check based on penetrating power and photon energy confirms that only X-rays combine deep tissue penetration with strong bone absorption, so X-rays are correctly identified.