In 1700 there were two theories about the nature of light. A theory of Sir Isaac Newton, proposed that light from a stream of tiny particles called corpuscles. The other theory, by Christiaan Huygens, said that light waves. Who was right? Now most of the evidence on the waves, but there was more to the story.
By 1800, most scientists accepted the wave theory of light, because the work of Thomas Young and James Clerk Maxwell. Both men were able to show that light diffracts, and Maxwell developed four famous formulas explained that the behavior of light as a wave. Thus the wave theory, the theory prevail.
However, in early 1900 is the work of Max Planck, Arthur Compton, and Albert Einstein showed that light has particle properties as well. Today we accept a wave-particle duality of light concept.
light as a wave
If you light a fire in a fireplace you can see and feel electromagnetic radiation. The fire is light (visible radiation) and heat (thermal radiation). Both types of radiation exist in the form of electromagnetic waves and each particle. That is why we need to understand particle and wave properties.
phenomena such as colors in soap bubbles, oil film and the rainbow are best explained if light as a wave. So, let's look at the components of a wave.
An electromagnetic wave consists of an electric wave and a magnetic wave traveling together at right angles to each other. The distance between adjacent maxima of the electromagnetic wave is the wavelength (λ) and half of the maximum distance of at a minimum, the amplitude. The number of cycles (maximum), by one point in a certain amount of time is known as the frequency (ν) and Hertz (Hz) is defined as one cycle per second.
The Spectrum
Unlike other types of waves, electromagnetic waves do not require a medium to travel and electromagnetic waves can be sent through a vacuum at 3.00 x 108 m /s, " the speed of light. " It is known that the speed of a wave is the product of the wavelength and frequency, and since the speed of light is constant, the wavelength (λ) and frequency (ν) must be inversely proportional.
- the shorter the wavelength, the higher the frequency
- the longer the wavelength the lower the frequency
The spectrum of electromagnetic wavelengths of radiation is the electromagnetic spectrum, ranging from very short wavelengths (cosmic radiation) to very long wavelengths ( thermal waves). Visible electromagnetic radiation (white light) is a very small region of the electromagnetic spectrum that spans from 750 nm to about 350 nm
Visible light can be integrated into its wavelengths by it through a prism. The prism bends the light (refraction), as the light and produces a complete range of colors (wavelengths) called a continuous spectrum.
All light can be split into component wavelengths by a spectrometer, but not all radiation producing a continuous spectrum. Many types of radiation of certain wavelengths are missing, and create a line spectrum. A line spectrum is a spectrum with bright lines, which only certain wavelengths.
light as particles
Although the wave theory of light seemed to answer many of the issues related to light, there are certain phenomena which could not be explained by this idea. Phenomena such as the photoelectric effect and the Compton effect pointed to the possibility of light as particles.
Then in 1900, a German physicist, Max Planck, proposed that light was not a continuous flow of energy, but consisted of small packets of energy (quantum), in whole number amounts (quantized).
Planck developed an equation to support his quantum theory using data gathered from studying the frequency and energy of different wavelengths. By comparing the frequencies and energies of the wavelengths, Planck not only realized they were directly proportional, but he was able to calculate the value of proportionality constant (Planck constant).
-Planck theory was not well accepted, however, until a young Swiss patent clerk successfully used quantum theory in his explanation of the photoelectric effect.
the photoelectric effect
The photoelectric effect was a phenomenon known for sometime. It was first described by Thomas Edison and is sometimes called the Edison Effect in his honor. This effect occurs when light on the surface of a clean metal and electrons are ejected from the surface.
In 1905, Albert Einstein used the quantum theory to help explain the photoelectric effect and show that electromagnetic radiation has particle properties as well. Starting with his own equation E = mc2, and then replace Planck's equation for energy, Einstein was able to show that a quantum energy has mass. In fact, the higher the energy the greater the mass and the more it was like a particle. Therefore, Einstein as a quantum of a photon.
wave-particle duality
Quanta, now called photons, light particles of his properties. The photon is a special "HUNK" Energy is directly proportional to the frequency, inversely proportional to its wavelength and can only be absorbed or released completely integer amounts (quantized). If the energy is the wavelength is short and the photons as particles, but if the energy is low the wavelengths are long and the photons as a wave.
Therefore, light has a wave - particle duality. If you would like to learn more about chemistry preparation go to http://yourCHEMcoach.com
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