Written by the Fiveable Content Team • Last updated September 2025
Verified for the 2026 exam
Verified for the 2026 exam•Written by the Fiveable Content Team • Last updated September 2025
Definition
The speed at which light travels in vacuum. It's approximately 299,792 kilometers per second or about 186,282 miles per second.
Related terms
Light-year: A unit of astronomical distance equivalent to the distance that light travels in one year, which is 9.461 trillion kilometers or about 5.879 trillion miles.
Electromagnetic spectrum: The range of all types of electromagnetic radiation, including visible light, radio waves, and X-rays. The speed of light applies to all these forms of radiation.
This is a particle representing a quantum of light or other electromagnetic radiation. It carries energy proportional to the radiation frequency but has zero rest mass.