What is Light?
Light is a Form of Electromagnetic Radiation
Light and Matter Fundamentals Light is a manifestation of electromagnetic force. Matter is composed of charged particles, or atoms, which consist of a nucleus surrounded by negatively charged electrons in motion. The source of visible light and all other forms of electromagnetic radiation is the atom. The charged nuclei in molecules move with respect to each other and when charged particles are in motion, an electromagnetic force is generating that will change with time.
Light and Matter Fundamentals Light is an electromagnetic field, or wave, that is oscillating.
Light and Matter Fundamentals Light is a wave that can be characterized by a frequency, wavelength and amplitude.
Light and Matter Fundamentals Light is also a particle, called a photon, as demonstrated by the photoelectric effect. Each photon carries a certain amount or packet of energy that is directly proportional to its frequency and inversely proportional to its wavelength.
Light and Matter Fundamentals Matter, composed of atoms or molecules, can absorb or emit the energy from a photon.
Light and Matter Fundamentals Electromagnetic radiation with very low frequencies (or long wavelengths, such as radio waves) is made up of photons that have relatively low amounts of energy, and therefore, generate low response levels when they interact with matter.
Very Large Array (VLA), New Mexico
Light and Matter Fundamentals Electromagnetic radiation with higher frequencies in the range of one gigahertz and with relatively shorter wavelengths corresponds to microwaves. Microwaves contain enough energy to make molecules in matter move or rotate faster, thereby producing heat.
Light and Matter Fundamentals An image of Earth in infrared wavelengths shows relative temperatures around the world. The photo includes a plume of carbon monoxide pollution near the Rim Fire that burned near Yosemite National Park in California on Aug. 26, 2013 (Credit: NASA/JPL-Caltech/Space Science Institute ).
Light and Matter Fundamentals Visible light is confined to a very narrow energy range of the electromagnetic spectrum between infrared light, with lower frequencies, and ultraviolet light, with higher frequencies.
Fluorescent minerals emit visible light when exposed to ultraviolet light
Light and Matter Fundamentals Electromagnetic radiation with very high frequencies and very short wavelengths, such as gamma rays, has enough energy to make molecules stretch and bend their bonds.
Light and Matter Fundamentals Reflection, refraction, diffraction and interference are phenomena observed with all electromagnetic waves.
Light and Matter Fundamentals For some molecules, photons in the visible light spectrum have enough energy to excite electrons, thereby promoting them to higher energy levels. Since these molecules will only absorb a specific frequency, what reaches our eye is no longer pure white light, but is now colored light. The color of the light we see corresponds to the energy level of pure white light minus the energy level of the color in the electromagnetic spectrum that the molecule absorbed.
Light and Matter Fundamentals
Light pollution excessive light that obstructs our view of the solar system and beyond and wastes energy.
Environmental Applications & Implications of Light-Matter Interactions Photodegradation and photo-oxidation of plastics not necessarily a good thing; plastic does not completely biodegrade but is merely broken apart into smaller and smaller pieces, which are can be cause for greater concern in the natural environment by creating a plastic soup.
Environmental Applications & Implications of Light-Matter Interactions UV sterilization and disinfection of water:
Safe drinking water for all. Solar Water Disinfection UV-A interferes directly with the metabolism and destroys cell structures of bacteria. UV-A (wavelength 320-400 nm) reacts with oxygen dissolved in the water and produces highly reactive forms of oxygen (oxygen free radicals and hydrogen peroxides) that are believed to damage pathogens. Cumulative solar energy (including the infrared radiation component) heats the water. If the water temperatures rises above 50 C, the disinfection process is three times faster.
Solar Water Disinfection
Solar Water Disinfection
Solar Power Conversion of light energy into usable electricity.
Solar Power Solar power is produced by collecting sunlight and converting it into electricity using photovoltaic systems, which are typically flat panels made up of many individual solar cells. Photovoltaic systems convert sunlight into electric current using the photoelectric effect. Electricity can also be produced using concentrated solar power systems, which use mirrors to focus a large area of sunlight into a small, powerful beam of light. Solar applications range from powering your scientific calculator to powering your home and to powering giant photovoltaic array systems designed to deploy power to energy grids.
Solar Power
Solar Power
Light Matter Interactions: More Information: http://www.youtube.com/watch?v=6g0sxwwqikc Light Pollution: http://ngm.nationalgeographic.com/2008/11/light-pollution/klinkenborg-text Photodegradation and Marine Pollution: http://ec.europa.eu/environment/water/marine/pollution.htm Safe Drinking Water For All: http://www.sodis.ch/index_en
Solar Power: http://www.solarpower.org More Information: http://www.solarhome.org http://www.solarenergy.org http://www.solarpowerinternational.com/2012/public/enter.aspx
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