Light is a fundamental part of our world. The uses of light are endless, it can be used to transmit data, change the mood of a space, perform surgery, and cook food. Light is the reason we see the world the way we do, but what is light?

History

People have attempted to explain light in many different ways. The earliest idea, held by Ptolemy, Euclid, and Hero, was that, “the rays [of light] originate in the eyes and travel to the object that is seen” (Physics). This was the accepted idea, until the 10th century when Alhazen discovered that, “light rays are emitted by a luminous source and are then reflected by objects into the eyes” (Physics). Seven hundred years after Alhazen, Newton discovered that white light was made of a combination of all the colors. Newton also claimed that light was made up of a “stream of particles” (Physics). This was challenged by Huygens, who said that light was made of waves. Huygens was later proven to be correct by Fresnel.
Radio waves, gamma rays, x-rays, and light are waves that make up the electromagnetic spectrum. Waves are forms of vibrations and are not made of matter. The difference between them is wavelength and frequency. Wavelength is the distance between two crests of the wave, and frequency, measured in hertz, is the number of times the wave oscillates between crests per second. These can be expressed in relation of one another as , where is velocity, is frequency, and is wavelength. Waves are infinitely dispersing. For example a flame of a candle, it radiates waves of light, and from the waves radiates different smaller waves and from those the process continues infinitely. Keep Reading