ultra-violet

Ultra-violet light from the sun causes some materials to glow.

Definition

1. Adjective:
   • Relating to electromagnetic radiation with wavelengths shorter than visible light: "ultra-violet" describes the type of radiation that lies beyond the violet end of the visible spectrum, having wavelengths from about 10 to 400 nanometers. It is invisible to the human eye but can have biological and chemical effects, such as causing sunburn.

Usage Examples

• (The invisible radiation from sunlight that causes sunburn.)
• (A type of light that kills bacteria and germs.)
• (A light source that shows hidden details.)

Advanced Usage

• "ultra-violet radiation": a specific term for the electromagnetic waves themselves.

  • Exposure to excessive ultra-violet radiation increases the risk of skin cancer. (Harmful electromagnetic energy from the sun or artificial sources.)

• "ultra-violet index": a scale that measures the strength of ultra-violet radiation from the sun at a particular place and time.

  • The weather report gave a high ultra-violet index today, so you should wear sunscreen. (A number indicating how strong the sun's UV rays are.)

Variants and Related Words

• Ultraviolet (adj): a common alternative spelling (without the hyphen) of "ultra-violet".

  • Ultraviolet lamps are used in tanning beds. (Same meaning as ultra-violet, referring to light beyond violet.)

• UV (abbreviation): the standard abbreviation for "ultra-violet".

  • UV rays are most intense between 10 a.m. and 4 p.m. (Short form for ultra-violet rays.)

Synonyms

• Invisible light: light that cannot be seen by the human eye.
• Black light: a type of ultra-violet lamp that emits long-wave UV radiation, often used for special effects.

Related Idioms

• No common idioms are associated with "ultra-violet", as it is a technical term. However, in popular culture, "ultra-violet" sometimes appears in phrases like:
  • "Under the ultra-violet light": meaning to examine something with special scrutiny or to reveal hidden truths.

    • The detective looked at the document under ultra-violet light to find the hidden watermark. (Using special light to uncover secret details.)