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The Interaction of Light with Biological Molecules
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The Nature of Light
Light consists of packets of energy that stream constantly from the sun in all directions. These packets are called photons. Each photon is a discrete entity of electromagnetic radiation with a characteristic frequency of electromagnetic field vibration and a wavelength. The wavelength and frequency of a photon are directly related to the energy. For any two photons, the one with more energy is the one that has the highest frequency of vibration. Since it is easier to measure the wavelength than the frequency of field vibration, the energy of light us usually described as wavelength. For visible light, units of nm (10-9 meters) are most common. The shorter the wavelength, the greater the frequency of a photon and the greater its energy.
Electromagnetic radiation such as ultraviolet light, x-rays and gamma radiation, have shorter wavelengths than visible light. These shorter wavelengths lead to much more energy per photon, giving them the energy potential for damaging biological molecules and tissues and are considered health hazards. Electromagnetic radiation with wavelengths longer than 700 nm include infrared light, microwaves, radar, TV and radio transmissions. This radiation has lower energy and therefore less potential to damage biological molecules and tissues. |
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