1. Visible light is a specific range of electromagnetic radiation that can be perceived by the human eye, with wavelengths between 400-700 nanometres (nm) and frequencies of 750-420 terahertz. 2. The term "light" in physics can refer to electromagnetic radiation of any wavelength, including gamma rays, X-rays, microwaves, and radio waves. 3. The primary properties of light are intensity, propagation direction, frequency or wavelength spectrum, and polarization. Its speed in a vacuum is one of the fundamental constants of nature, estimated at 299792458 m/s. 4. All electromagnetic radiation exhibits properties of both particles and waves, with single, massless particles called photons detectable with specialized equipment. 5. The main source of natural light on Earth is the Sun, while historically, fire (from campfires to kerosene lamps) has also been an important source of light for humans. 6. The development of electric lights and power systems has led to electric lighting effectively replacing firelight in many everyday interactions.