cahaya

Cahaya is the Indonesian term for visible light, the portion of electromagnetic radiation that can be detected by the human eye. In physics, light is described as both a wave and a stream of particles called photons. In vacuum, light travels at approximately 299,792 kilometers per second, and its visible portion spans roughly 380 to 750 nanometers in wavelength. Light can be produced by natural sources such as the Sun, stars, fire, and bioluminescent organisms, as well as artificial sources including electric lamps, LEDs, and lasers.

When light encounters matter, it may be reflected, refracted, absorbed, or scattered. These interactions give rise to color, transparency, and various optical effects. Lenses and prisms manipulate light to form images or separate colors through refraction and dispersion. Humans perceive light through the eye, with brightness described by luminance and measured in lumens or lux, while color is determined by wavelength. In everyday Indonesian usage, cahaya also carries metaphorical meanings such as brightness, enlightenment, or hope, and the term appears widely in literature, poetry, and religious or cultural contexts.