## Light

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##### 1. Electromagnetic Waves
What surrounds you and bombards you constantly? Most of it is invisible but you can’t imagine living without it. It is electromagnetic radiation, a type of energy commonly known as light. This energy is produced by the vibration of charged particles. As charged particles move back and forth, the electric field around it vibrates creating a vibrating magnetic field. The two vibrating fields, which are at right angles to each other, produce electromagnetic waves. These waves can travel through materials as well as a vacuum. All electromagnetic waves travel at the incredible speed of about 300,000 km/s in a vacuum, often called the speed of light. This speed is equal to the wavelength of light times its frequency and is represented by the equation c = wavelength x frequency.
##### 2. Light: Wave or Particle
Most of us think of light as a wave. Waves easily explain interactions such as reflection. However, early in the 20th century, some scientists noticed that light hitting a metal surface can sometimes eject electrons. How can light waves do this? Albert Einstein showed this can only happen if light is made up of tiny particles called photons. Einstein revolutionized physics by describing light as photons. Scientists now believe light exhibits both wave and particle properties.
##### 3. Electromagnetic Spectrum
Although every electromagnetic wave travels at the same speed, each can have a different wavelength and frequency. The electromagnetic spectrum organizes the types of light by decreasing wavelength and increasing frequency, from left to right. It includes radio waves, microwaves, infrared light, visible light, ultraviolet light, x-rays, and gamma rays. The energy of the electromagnetic wave is also related to wavelength and frequency. Energy is directly proportional to frequency and inversely proportional to wavelength. Higher frequency, shorter wavelength waves have higher energy. The wave energy increases from left to right across the spectrum. On the spectrum, radio waves have the lowest energy while gamma rays have the highest energy.