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12 June 2011 Last updated at 20:42 ET By Jason Palmer Science and technology reporter, BBC News The single-cell lasers were less than 20 millionths of a metre across A single living cell has been coaxed into producing laser light, researchers report in Nature Photonics . The technique starts by engineering a cell that can produce a light-emitting protein that was first obtained from glowing jellyfish. Flooding the resulting cells with weak blue light causes them to emit directed, green laser light.
Whether they know it or not, anyone who's ever gotten a speeding ticket after zooming by a radar gun has experienced the Doppler effect – a measurable shift in the frequency of radiation based on the motion of an object, which in this case is your car doing 45 miles an hour in a 30-mph zone. But for the first time, scientists have experimentally shown a different version of the Doppler effect at a much, much smaller level – the rotation of an individual molecule. Prior to this such an effect had been theorized, but it took a complex experiment with a synchrotron to prove it's for real. "Some of us thought of this some time ago, but it's very difficult to show experimentally," said T.
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Computer circuits and nanodevices are already smaller than that, and getting still smaller. The key is figuring out how to guide near-field light, which forms a standing field rather than light's usual moving wave. Near-field light is produced by shining light through a tiny hole or lens that is positioned closer to a surface than the wavelength of the light; its size is limited by the hole or lens size rather than the wavelength of the light. When light is farther away from a surface, it can only be focused to about half its wavelength.
Visible light is a complex phenomenon that is classically explained with a simple model based on propagating rays and wavefronts, a concept first proposed in the late 1600s by Dutch physicist Christiaan Huygens. Electromagnetic radiation, the larger family of wave-like phenomena to which visible light belongs (also known as radiant energy ), is the primary vehicle transporting energy through the vast reaches of the universe. The mechanisms by which visible light is emitted or absorbed by substances, and how it predictably reacts under varying conditions as it travels through space and the atmosphere, form the basis of the existence of color in our universe.
Fluorescence activity can be schematically illustrated with the classical Jablonski diagram, first proposed by Professor Alexander Jablonski in 1935 to describe absorption and emission of light. This tutorial explores how electrons in fluorophores are excited from the ground state into higher electronic energy states and the events that occur as these excited molecules emit photons and fall back into lower energy states. To operate the tutorial, first select an absorption and emission mechanism (fluorescence, phosphorescence, or delayed fluorescence) by toggling through the choices presented in the pull-down menu. Next, click on the start button with the mouse to induce a virtual electron to absorb energy and be promoted to a higher energy level. After the electron arrives at the higher energy level, it will then decay in a manner typical of the selected excitation mechanism.
Electrons can absorb energy from external sources, such as lasers, arc-discharge lamps, and tungsten-halogen bulbs, and be promoted to higher energy levels. This tutorial explores how photon energy is absorbed by an electron to elevate it into a higher energy level and how the energy can subsequently be released, in the form of a lower energy photon, when the electron falls back to the original ground state. In order to operate the tutorial, first choose an exciting wavelength by using the mouse cursor to translate the Wavelength (or Energy ) slider to the desired position. Next, use the mouse to press the blue Pulse button, which will excite the atom by absorption of a photon of the chosen wavelength.
Electromagnetic radiation, the larger family of wave-like phenomena to which visible light belongs (also known as radiant energy ), is the primary vehicle transporting energy through the vast reaches of the universe. This interactive tutorial explores the classical representation of an electromagnetic wave as a sine function, and enables the visitor to vary amplitude and wavelength to demonstrate how this function appears in three dimensions. The tutorial initializes with a sine function simulating electromagnetic wave propagation traversing from left to right across the window. The oscillating electric field vectors of the virtual electromagnetic wave are represented by blue lines, while the magnetic field vectors are depicted in red. In order to operate the tutorial, use the mouse cursor to drag the wave back and forth in the window to observe how it appears from different angles.
Light is a complex phenomenon that is classically explained with a simple model based on rays and wavefronts. The Olympus Microscopy Resource Center Microscopy Primer explores many of the aspects of visible light starting with an introduction to electromagnetic radiation and continuing through to human vision and the perception of color. Each section outlined below is an independent treatise on a limited aspect of light and color.
The exact nature of visible light is a mystery that has puzzled man for centuries. Greek scientists from the ancient Pythagorean discipline postulated that every visible object emits a steady stream of particles, while Aristotle concluded that light travels in a manner similar to waves in the ocean. Even though these ideas have undergone numerous modifications and a significant degree of evolution over the past 20 centuries, the essence of the dispute established by the Greek philosophers remains to this day. One point of view envisions light as wave-like in nature, producing energy that traverses through space in a manner similar to the ripples spreading across the surface of a still pond after being disturbed by a dropped rock.