Definition

1. Noun:
   • A unit of illumination: A phot is a unit of illuminance or illumination, equal to one lumen per square centimeter. It is a metric unit used in photometry to measure the amount of light falling on a surface.

Usage

• The "phot" is a technical unit primarily used in scientific and engineering contexts, particularly in physics and lighting design. It is not commonly used in everyday language. One phot is equivalent to 10,000 lux.

Examples

• Noun:
  • The surface received an illumination of two phots.
  • Older photometry texts sometimes express brightness in phots rather than lux.

Advanced Usage

• "Milliphot": A subunit equal to one-thousandth of a phot.
  • The very dim light was measured in milliphots.

Variants and Related Words

• Illuminance (n): The quantity of light falling on a surface per unit area; phot is a unit of illuminance.
• Lux (n): The SI unit of illuminance, equal to one lumen per square meter. 1 phot = 10,000 lux.
• Lumen (n): The SI unit of luminous flux, a measure of the total quantity of visible light emitted by a source.

Synonyms

• Unit of illuminance: This is a descriptive synonym, as "phot" is a specific, named unit.

Notes

• The word "phot" is derived from the Greek word 'phōs' (φῶς), meaning "light".
• In modern practice, the SI unit lux has largely superseded the phot in most scientific and technical fields.

Noun

1. a unit of illumination equal to 1 lumen per square centimeter; 10,000 phots equal 1 lux