In physics, light is a form of electromagnetic radiation that is visible to the human eye, typically within the wavelength range of about 400 to 700 nanometers (nm). However, the term "light" is often used more broadly to refer to the entire electromagnetic spectrum, which includes radio waves, microwaves, infrared, ultraviolet, X-rays, and gamma rays.
Key Properties of Light:
Dual Nature:Light exhibits both wave-like and particle-like properties.
Wave theory: Light behaves like a wave, showing properties such as interference, diffraction, and polarization.
Particle theory (Quantum theory): Light can also be thought of as a stream of particles called photons, each carrying a discrete amount of energy (quantum).
Speed:In a vacuum, light travels at a constant speed of approximately 3.00 × 10⁸ meters per second (m/s).
Wavelength and Frequency:The color of visible light depends on its wavelength or frequency.
Violet light has shorter wavelengths (~400 nm) and higher frequency.
Red light has longer wavelengths (~700 nm) and lower frequency.
Energy:The energy of a photon is given by the equation:E = h × f,where E is energy, h is Planck’s constant, and f is the frequency of light.
Electromagnetic Nature:Light consists of oscillating electric and magnetic fields that propagate perpendicular to each other and to the direction of the wave’s travel.
Light in Different Contexts:
Classical Physics: Described as a wave (Maxwell’s equations).
Quantum Physics: Described as photons with quantized energy.
Relativity: Light speed is the ultimate speed limit in the universe, and its constancy is a foundation of Einstein’s theory of relativity.
