14.4 - UV Light

UV security marking and forgery detection

Some inks glow under UV light but are invisible in ordinary light, making UV useful for security marking.

Security marking

• A security pen can write details such as a postcode on valuable property.
• The mark can't be seen in normal light, but shows up under a UV lamp to help identify stolen property.

Detecting forgeries

Genuine bank notes and passports carry special markings that only appear under UV light to help detect fakes.

Dangers of ultraviolet radiation

• UV damages the surface cells of the skin and can cause premature ageing.
• Some UV is ionising - it carries enough energy to knock electrons off atoms.
  • This can disrupt the DNA in skin cells, causing mutation and leading to skin cancer.
• UV can also harm the eyes, causing eye conditions and even blindness.

Reducing the risk

• Wear sunscreen with UV filters in strong sunlight.
• Limit the time spent in strong sunlight.

Sterilising with UV

• Ultraviolet radiation kills bacteria and viruses, so it can be used to sterilise.
• UV sterilises water by killing bacteria, making it safe to drink.
• It's also used in hospitals to sterilise surgical equipment.