Describe the harmful effects on people of excessive exposure to electromagnetic radiation, including: (a) microwaves; internal heating of body cells (b) infrared; skin burns (c) ultraviolet; damage to surface cells and eyes, leading to skin cancer an

Published by Patrick Mutisya · 8 days ago

IGCSE Physics 0625 – Electromagnetic Spectrum: Harmful Effects

3.3 Electromagnetic Spectrum – Harmful Effects of Excessive Exposure

Electromagnetic (EM) radiation spans a wide range of wavelengths and frequencies. While many parts of the spectrum are harmless at normal levels, excessive exposure can damage biological tissue. The following notes describe the main health risks associated with four important regions of the spectrum.

Microwaves (≈ 1 mm – 1 m, 300 MHz – 300 GHz)

Microwaves are absorbed mainly by water molecules in the body, causing rapid internal heating.

  • Energy is converted to heat within cells, raising temperature.

  • Prolonged or intense exposure can lead to:

    • Thermal stress on organs.

    • Disruption of normal cellular processes.

    • Potential tissue damage if core temperature exceeds safe limits (≈ 42 °C).

  • Typical sources: microwave ovens, radar, some wireless communication devices.

Infrared Radiation (≈ 700 nm – 1 mm, 300 THz – 300 GHz)

Infrared (IR) is felt as heat and is absorbed primarily by the outer layers of the skin.

  • High‑intensity IR can cause superficial burns.

  • Burn severity depends on exposure time and power density.

  • Common sources: heating lamps, industrial furnaces, solar radiation.

Ultraviolet Radiation (≈ 10 nm – 400 nm, 750 THz – 30 PHz)

U \cdot radiation is energetic enough to break chemical bonds in molecules, affecting surface cells and the eyes.

  • UV‑A (315–400 nm): deep skin penetration, contributes to premature ageing.

  • UV‑B (280–315 nm): causes sunburn, DNA damage in epidermal cells → skin cancer risk.

  • UV‑C (100–280 nm): mostly absorbed by the ozone layer; artificial sources (e.g., germicidal lamps) can cause severe burns and eye injury.

  • Eye conditions include photokeratitis and cataract formation.

X‑rays and Gamma Rays (≈ 0.01 nm – 10 nm, > 30 PHz)

These high‑energy photons have enough energy to ionise atoms, producing direct damage to DNA and other cellular structures.

  • Ionisation can create free radicals that break DNA strands.

  • Consequences:

    • Cellular mutations → increased cancer risk.

    • Acute radiation syndrome at very high doses.

    • Long‑term effects such as leukemia and other malignancies.

  • Sources: medical imaging (X‑ray, CT), industrial radiography, cosmic rays, nuclear reactions.

Summary of Harmful Effects

Region of SpectrumTypical Wavelength / FrequencyPrimary Biological EffectCommon SourcesHealth Outcome of Excessive Exposure
Microwaves1 mm – 1 m
300 MHz – 300 GHz		Internal heating of body cellsMicrowave ovens, radar, Wi‑Fi, mobile phonesThermal injury, organ dysfunction if temperature > 42 °C
Infrared700 nm – 1 mm
300 THz – 300 GHz		Surface heating → skin burnsHeating lamps, industrial furnaces, solar IRFirst‑degree to third‑degree burns
Ultraviolet10 nm – 400 nm
750 THz – 30 PHz		DNA damage in surface cells; eye damageSunlight, tanning beds, U \cdot lampsSunburn, skin cancer, cataracts, photokeratitis
X‑rays / Gamma rays0.01 nm – 10 nm
> 30 PHz		Ionisation of atoms → DNA mutationsMedical imaging, industrial radiography, cosmic raysCellular mutation, cancer, radiation sickness

Suggested diagram: Electromagnetic spectrum showing wavelength ranges and typical sources for microwaves, infrared, ultraviolet, X‑rays and gamma rays.

Key Points to Remember

  1. Energy of EM radiation increases as wavelength decreases.

  2. Biological damage correlates with the ability of photons to penetrate tissue and ionise atoms.

  3. Protective measures (e.g., shielding, sunscreen, limiting exposure time) are essential for high‑energy regions.

  4. Understanding the specific hazards helps in applying safety guidelines in both everyday life and occupational settings.