Light and other forms of energy, including sound, are measured by its wavelength and frequency. Wavelength multiplied by frequency is equal to the speed of light. The relationship between wavelength and frequency is that they are inversely proportional to one another. That is to say that if one increases, the other one gets smaller, therefore to higher frequencies correspond lower wavelengths, and to lower frequencies will correspond longer wavelengths. The electromagnetic spectrum produces radiating energy of varied wavelengths and frequencies.
How light is measured
Light travels in empty space at the speed of ¨c¨ or 299,792,558 meters (186,282 miles)/second. This is the greatest speed at which matter and energy can travel in the universe. Light, like other forms of energy, such as seismic waves, sound waves, or any other forms of vibrating waves, is measured by the relation between wavelength and frequency of its waves. Thus, wavelength multiplied by frequency is equal to the speed of light, and this is the speed at which light travels in all forms of energy in the electromagnetic spectrum. The speed of light varies when entering a medium such as water or glass and is called the refractive index.
Wavelength and frequency
Electromagnetic radiation is transmitted through space in the form of waves. These waves can be compared to those formed in a water pond when you throw a rock inside. Waves are composed of crests and troughs, which correspond to high and low peaks, respectively. The distance from crest to crest is known as the wavelength, and the distance from the undisturbed state of the wave to the crest is the amplitude of the wave. The periodicity at which the wave passes through a given point is its frequency and is measured in Hertz. Wavelength and frequency are inversely proportional to one another, meaning that when one increases the other diminishes. In electromagnetic radiation, high frequency radiation waves correspond to lower wavelengths.
The electromagnetic spectrum
The electromagnetic spectrum comprises all kinds of radiation, including radio waves, infrared light, visible light, ultraviolet light, x-rays and gamma rays. All this forms of energy are transmitted through space at the speed of light and in the form of fluctuating waves. The periodicity of these waves is measured in Hertz. The difference between radio waves, which lie at the lower end of the electromagnetic spectrum, and gamma rays at the opposite end of the spectrum is their wavelength and frequency. Radio waves produce long waves, ranging from millimeters to meters in size at very low frequencies, measured in between megahertz to gigahertz, whereas, gamma rays produce very short wavelengths and high frequencies, and are measured in the nanoscale.
Speed of light in a medium
The speed of light waves in a medium, such as glass or water is less than the speed of light through a vacuum, such as empty outer space. The ratio between the speed of light in empty space and the speed of light in a substance is known as the refractive index. Thus, c/v = n, where c is the speed of light in a vacuum; v is the speed of light in a substance and n is the refractive index. Typically, n is the factor by which the wavelength and speed of radiation is reduced compared to the speed and wavelength in a vacuum. The refractive index of materials, known as dispersion, varies with the wavelength and frequency of light.