1. A unit of frequency equal to one quadrillion hertz (10¹⁵ Hz), used to measure electromagnetic radiation in the infrared and visible light spectrum.
Usage: technical; physics; abbreviation: PHz

Examples

• Visible light has frequencies in the range of hundreds of terahertz to several petahertz.
• Infrared radiation typically falls between 10 terahertz and 430 petahertz.
• Scientists use petahertz measurements to study the properties of ultraviolet light.
• The petahertz range is essential for understanding optical phenomena in materials science.