Electromagnetic Waves: Safety and Dangers

Electromagnetic (EM) waves are a family of waves that all travel at the same speed in a vacuum, about $3.0 \times 10^8\ \text{m s}^{-1}$. They differ in wavelength and frequency. Higher frequency waves carry more energy and are generally more harmful.

How EM waves can harm

• Heating: waves like microwaves and infrared transfer energy to body tissues, raising temperature (like a microwave oven heating food).
• Ionisation: higher-frequency waves (ultraviolet, X-rays, gamma rays) have enough energy to knock electrons off atoms in cells. This can damage DNA, causing mutations and possibly cancer.

Key risks and protections by region

• Microwaves (e.g., mobile phones, microwave ovens): can cause internal heating of body cells. Protection: increase distance, limit exposure time; oven doors have metal mesh shielding to keep microwaves in.
• Infrared (e.g., heaters, grills): can cause skin burns. Protection: avoid close, intense sources; use heat-resistant gloves and barriers.
• Ultraviolet (UV) (sunlight, UV lamps): damages surface cells and eyes; can lead to sunburn, skin cancer, and eye conditions. Protection: shade, clothing, SPF 30+ sunscreen, UV-blocking sunglasses.
• X-rays (medical imaging, security): ionising; can cause mutations or cell damage. Protection: only use when needed; wear lead aprons; stand behind protective screens.
• Gamma rays (radioactive sources, cancer treatment): very penetrating and ionising; can damage or kill cells. Protection: reduce exposure time, increase distance, use thick shielding (lead or concrete).
• Visible light and radio waves: usually safe at normal levels, but very bright light can damage eyes. Do not look directly at the Sun.

Reducing exposure

• Time: shorter exposure lowers risk.
• Distance: stand further from the source; intensity drops with distance.
• Shielding: use barriers that absorb or block the waves (e.g., sunscreen for UV, lead for X-rays).

Common misconceptions

• “All radiation is radioactive.” False: most EM waves are not from radioactive materials. Only high-frequency EM (UV, X-rays, gamma) is ionising.
• “Microwave ovens leak dangerous radiation.” The metal mesh in the door reflects microwaves back inside when undamaged.