The Role of the Sun's Electromagnetic Radiation in the Biosphere
Electromagnetic radiation
Electromagnetic radiation is energy that travels as oscillating waves through space and includes radio waves, infrared, visible light, ultraviolet, X-rays and gamma rays.
- The Sun emits electromagnetic (EM) radiation across a continuous spectrum, ranging from low-frequency radio waves to high-frequency gamma rays.
- Different wavelengths carry different levels of energy, which determines their biological significance and potential to cause harm.
- The portion of solar radiation reaching Earth depends on atmospheric absorption and reflection.
Types of Solar Radiation Relevant to the Biosphere
- Infrared radiation warms the Earth’s surface and atmosphere, helping to maintain global temperatures suitable for life.
- Visible light supports photosynthesis and therefore determines the productivity of terrestrial and aquatic ecosystems.
- Ultraviolet (UV) radiation can be damaging to living organisms due to its high energy.
| Radiation Type | Wavelength Range | Major Source |
|---|---|---|
| Infrared (IR) | ~700 nm – 1 mm | Sun, Earth’s emitted energy |
| Visible Light | 400 – 700 nm | Sun |
| Ultraviolet (UV) | 100 – 400 nm | Sun |
Visible light is like the fuel that powers ecosystems, while UV radiation is like an overcharge of energy that can burn or destroy biological tissues.
UV Categories and Biological Risk
- UV radiation has shorter wavelengths and higher frequencies, which means it carries more energy than visible or infrared radiation.
- The higher the frequency, the greater the potential to damage DNA, cells and tissues in living organisms.
- The UV spectrum is subdivided into three biologically relevant types:
| Type | Wavelength | Harm Level | Ozone Absorption | Key Effects |
|---|---|---|---|---|
| UVA | 315–400 nm | Least harmful | Mostly reaches Earth’s surface | Skin ageing and contributes to cancer |
| UVB | 280–315 nm | Highly harmful | Mostly absorbed but some reaches Earth | DNA mutation, skin cancer, sunburn |
| UVC | 100–280 nm | Extremely harmful | Completely absorbed by ozone | Would be lethal if it reached Earth |
- Many assume UVA is harmless because it causes tanning.
- UVA contributes to skin cancer, immune suppression, and premature aging.
Ozone depletion leads to higher amounts of UV-B radiation reaching the surface.
Stratospheric Ozone as a Protective Layer
Ozone
Ozone (O₃) is a reactive form of oxygen composed of three oxygen atoms that absorbs harmful ultraviolet radiation from the Sun.
- The ozone layer exists in the stratosphere, a region 16–35 km above the Earth’s surface.
- It plays a crucial role in protecting life by absorbing nearly all UVC radiation and most UVB radiation, which would otherwise reach the surface at dangerous intensities.
- Ozone is continually created and destroyed naturally, and its concentration varies geographically and seasonally.
Natural Formation and Maintenance of Ozone
- Ozone forms when oxygen molecules (O₂) are split by solar UV radiation into single oxygen atoms, which then combine with other O₂ molecules to form ozone (O₃).
- Ozone is constantly broken down and regenerated, creating a natural equilibrium that ensures harmful UV radiation remains controlled.
The amount of ozone is small in proportion to atmospheric gases, but it is essential because it protects nearly all life from high-energy UV radiation.
AnalogyThe ozone layer behaves like a global sunscreen, absorbing UV radiation before it reaches living organisms.
Theory of Knowledge- How does our understanding of the electromagnetic spectrum influence global policies on climate change and ozone protection?
- What ethical considerations arise when balancing human needs with environmental protection?
