UV

Ultraviolet Radiation

Ultraviolet (UV) radiation is a form of electromagnetic radiation with a wavelength shorter than that of visible light but longer than X-rays. It is present in sunlight and constitutes about 10% of the total electromagnetic radiation output from the Sun. UV radiation is also produced by electric arcs and specialized lights, such as mercury-vapor lamps, tanning lamps, and black lights.

Types of Ultraviolet Radiation

Ultraviolet radiation is divided into three main types based on wavelength:

• UVA (315-400 nm): Also known as long-wave UV, UVA accounts for approximately 95% of the UV radiation reaching the Earth's surface. It can penetrate deeper into the skin and is associated with skin aging and wrinkling.

• UVB (280-315 nm): Medium-wave UV, UVB is partially absorbed by the ozone layer and is responsible for causing sunburn. It plays a key role in the production of vitamin D in the skin.

• UVC (100-280 nm): Short-wave UV, UVC is mostly absorbed by the Earth's atmosphere and does not reach the surface. It is used in germicidal lamps for disinfection purposes.

Sources of Ultraviolet Radiation

The primary source of UV radiation is the Sun. However, artificial sources include:

• Tanning beds: Emit UVA and UVB radiation to induce tanning.
• Mercury-vapor lamps: Used in industrial processes and street lighting.
• Black lights: Emit UVA radiation and are used in artistic and forensic applications.
• Germicidal lamps: Emit UVC radiation for sterilization and disinfection.

Effects of Ultraviolet Radiation

Biological Effects

UV radiation has both beneficial and harmful effects on human health:

• Vitamin D synthesis: UVB radiation is essential for the production of vitamin D in the skin, which is crucial for bone health.
• Skin damage: Prolonged exposure to UV radiation can lead to skin damage, including sunburn, premature aging, and an increased risk of skin cancer.
• Eye damage: UV radiation can cause eye damage, such as cataracts and photokeratitis.

Environmental Effects

• Ozone layer depletion: The depletion of the ozone layer increases the amount of UVB reaching the Earth's surface, leading to increased health risks.
• Ecosystem impact: UV radiation can affect the growth and development of plants and aquatic organisms.

Protection Against Ultraviolet Radiation

To protect against the harmful effects of UV radiation, several measures can be taken:

• Sunscreen: Use broad-spectrum sunscreen with a high SPF to protect against UVA and UVB.
• Protective clothing: Wear hats, sunglasses, and long-sleeved clothing.
• Shade: Seek shade during peak sunlight hours.

Also see

• Electromagnetic spectrum
• Ozone layer
• Skin cancer
• Photoprotection