What is Light

Horace He

Last Updated: September 17, 2023

What is Light

Light, in the context of the lighting, refers to electromagnetic radiation that is visible to the human eye. It is a form of energy that enables us to perceive our surroundings and plays a crucial role in illumination and visual perception. Light can be emitted, absorbed, or reflected by various sources, both natural and artificial, such as sunlight, incandescent light bulbs, and flames.

The speed of light in vacuum is a fundamental constant, defined to be exactly 299,792,458 meters per second. This fixed value serves as a reference in scientific calculations. However, the speed of light can vary when it travels through different transparent substances containing ordinary matter. For example, in water, the speed of light is about 3/4 of its speed in vacuum.

Throughout history, scientists have conducted experiments to measure the speed of light. Early attempts were made by Galileo and Ole Rømer in the 17th century, with Rømer estimating a speed of 227,000,000 meters per second if he had known the exact size of Earth’s orbit. Subsequent experiments by Hippolyte Fizeau, Léon Foucault, and Albert A. Michelson further refined the measurement, leading to a precise value of 299,796,000 meters per second.

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