explain with the aid of diagrams,how a Pockel's Cell is used to Q-switch a laser,?
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You could go to the web site how stuff works, there they will give you diagrams of how it works.
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The link above dosn't give any usefull info its some product manual.\n\nall of these components use semi-conductors.\n\nA light dependent resistor is basicly what it names sugests, (it resists more as the amount of light falling on the semi-conductor material inside it increases). These are used in street lights and other such things and can be connected to relays wich can turn on and off circuits.\n\nA diode use two types of semi-conductor n and p(this means one has many "holes" and the othere dosn't (a hole implys a bond without an electron)) which are doped to a have an electric field that only allows current to flow in only one direction, These are useful for protecting other components like micro chips from being burnt by wrong flowing charge.\n\nA transitor uses three chunks of semi conductor in pnp or npn order, each pin on the bottom of a transitor is attached to each chunk. The transitor varys amplifys a signal with a very small current so are commonly used in things like radios for converting the electro magnetic wave to a sound wave. Transitors are also used in micro chips where (with modern technology) many thousands can be fitted in a just a square millemeter.\n\nIm sorry if my explanation seems a little breif but  the guys from AT&T how first descreibed semi-conductors got a Nobel prise and so far i havnt even got a physics AS.
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Howstuffworks has good diagrams and explanations that may help you.  Good luck.
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well if i am not wrong.. they work on the principle of thermionic emission... \n\nnow wat happens is ... at the cathode end ( negatively charged) there is a metal bit.. called emitter  and at the anode end( positive terminal) another metal called the receiver. the tube is vacuated and filled with gas, in this case a halogen vapour. \n\nwat happens is when a potential is applied, when we switch it on, the cathode emits electrons.\nthese electrons pass thru the vapours and ionise them. when ionised these gases emit energy in the form of light..\n\nthis is the explanation in the most condensed form... equations make it complicated for understanding... \n\nhope i did justice to ur query
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The blue-green is so it will penetrate the oceans.  (Water absorbs red and other colours).\n\nCommunications by lasers cannot be listened to by enemies or other parties unless they are directly in the beam's path.  Combined with encryption the laser communications are very secure.\n\nAlso the current VLF (Very Low Frequency) communication systems cannot transfer data very fast so even small messages can take many minutes to transmit.  Lasers are capable of very high data rates (just look at CDs and DVDs).
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http://science.howstuffworks.com/lightning.htm
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Not much to go on here, but the attached link runs through basic electrical circuitry in layman's language.\n\nBASIC CIRCUIT CONSTRUCTION\n1. Power Source (Battery, Alternator, Generator, etc.)\n2. Protection Device (Fuse, Fusible Link, or Circuit Breaker)\n3. Load Device (Lamp, Motor, Winding, Resistor, etc.\n4. Control (Switch, Relay, or Transistor)\n5. Conductors (A Return Path, Wiring to Ground)
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http://www.eas.asu.edu/~holbert/ece201/kvl.html
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It'd be pretty complicated, but one way might be...\n\nUse the radio waves to heat something.  Connect a heat engine between the warmed object and one at room temperature.  Use the heat engine to run a generator.  Use the generator to charge a battery, and then connect the battery to a light bulb (or laser, or some other thing that emits visible light).  Voila!\n\nAnother way you might be considering is something analogous to frequency doubling-- shine laser light of some wavelength on a crystal, and out from the other end comes laser light with double (or sometimes triple) the frequency.  This won't work with radio waves because they simply don't have enough energy.  Frequency doubling works because of nonlinear effects that take place in the crystal.  Radio waves are not energetic enough to produce nonlinear effects.
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1 Find the current flowing in the lamp.   P  = VI\n2 Look up the charge on an electron.     q\n\nDivide 1  by 2  which will give you the number of electrons flowing per second.      n  =  I/q
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Just goanna tell you why it is like that physically not mathematically but the math part I think you already know.\n\nFor starters there aren't any 2 level lasers there are 3 level lasers and 4 level lasers (4 levels is better then 3) never 2, you will understand why.\nNow first of all you have three processes:\nStimulated emission ;(SE)\nStimulated absorption ;(SA)\nSpontaneous emission;\nThe first two are absolutely symmetric they work with the same constants, they have just one difference, the SE is   proportional to the number of electrons in the exited state and SA proportional to the number of electrons in the fundamental (I do not consider empty places because in practice they aren't really important, don't know if you have saw them if not forget it). Now imagine your gain medium in the fundamental state, you pump it, the medium passes to have more electrons in the exited state, you pump it hard, so now what happens you have the 3 processes. The SA increases the population in the upper level and the SE in the lower level, the SA at first is more successful because there are more atoms in the fundamental state. But you arrive to a point where the population in the 2 levels is equal then both processes have the same intensity, that’s the limit of this system equal population, but you pump even stronger  trying to get an inversion population, what happens? Both process are equal in intensity the population will not vary, now let’s consider the third process. This is a less intense process if you pump well; this will just contribute to the population in the lower level, so you never arrive to have half the atoms in the upper state because even if the SA and SE are equal the spontaneous emission will create one more atom in the lower level.\n\nYou can never have population inversion in a 2 level system. There aren't any lasers with 2 levels, but you can do the calculations for. If you do not understand why population inversion is important here it goes:   you always have lost in your cavity, reflection in the gain medium, output coupler ...Only when you built a laser you see: there are "huge" losses in the laser everywhere. So you have to compensate that with a gain at every passage, well your gain medium only will have a gain > then 1 if you have population inversion, if not your medium will absorb and emit the same quantity having given 0 photons in plus to your system, So you will lose photons at every turn your light will end up really quickly.\n\nNow 3 level systems, in this systems you can pump really hard to the level 3 you can pump electrically by other means, you can pump it optically… but for instance imagine that the only thing getting out of 3 is the spontaneous decay from 3 to 2 only (which is possible, stimulated emission from 3 to 1 might not even be possible) then you can have more atoms in 2 then 1 you have population inversion. 3 level systems are the ruby, first laser ever built, and the Nd:Yag a very powerfull laser, used a lot \n\nIn relation to 4 levels 3 levels systems difference, there you can see the following, when you start to pump in the 4 level systems your base state (in relation to the emission line), is desert you have population inversion immediately, is easier to obtain gain.\n\nTo finalise this part of the answer I can tell you that getting energy out of a 2 level system would be like getting more energy then the one you input it would violate the thermodynamic law the energy conservation principle.\n\nThe second part of the question, I do not now if you where talking in the 2 level or in the 3 level system but I suppose it’s the 3 level system all the way.\nNow the answer to your question is one of most beautiful things that the basic laser physic has, remember you have medium and a cavity, this cavity reproduces it self times and times over. You need the source in 1 to 3 and you create population inversion, now your medium will emit in all directions b
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They are also used in pump-probe experiments-- if you want to measure things (atomic motion, for instance) on a very short time scale, you would need a very short pulse.  \n\nA pump-probe experiment uses one laser pulse to excite the sample, and then a second pulse is sent through the sample and some property of the pulse is measured i.e. transmission, reflectance, phase shift. as a function of the time interval between pulses.  From measurements at different times, you can determine the response of the sample to the laser pulse.
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You will need a laser diode. Other laser types (gas, solid state) usually have much larger cavities then a semiconductor laser, and therefore are much larger. As far as finding a laser diode, There are companies that make them, although the only one I know off the top of my head is Tyco, and they make laser diodes for fiber optic applications which are around 1 micrometer (wave length), which is in the infrared range. You'll have to do some searching. Other then the laser diode, a resistor (to control the current) and a voltage source (battery) should be all you need (I've never tried to actually make one, but I am an Electrical Engineering student).
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hum...not sure you can do that, however, if you want to have to beams (more or less the same as two different lasers, depending on the purpose of your experiment) in phase with each other, you can use something to split the beam (a beam splitter), and, with a coupla mirrors organized in a certain configuration, you should be able to have 2 lasers in phase
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In an electric torch the bulb glows when we switch on the circuit and bulb glows off when we switch off the circuit. \n\nGlowing of bulb is the indication that the current is in the circuit. When there is no current the bulb will not glow.\n\nWe use the cells (Battery) as long as it has life.  The cells have electric energy and they are used when we want. When it is not used, (switch off position) there is no current in the wire connecting the bulb.\n\nThe differences between this and the power supply through lines to the buildings are not much.\n\nIn the latter, instead of direct current, alternating current is used; instead of small power huge power is used.\n\nTherefore when the switch is in off position there is no current in the lines, but they are full of energy and at any time they can produce current when the switch is on.\n\nAn analogy with water tank may be useful.  Water is stored in the tank. Whenever we open the pipe water flows in the whole pipe connecting the tank and the end pipe, when we close the pipe no water flows but water pressure will be there.
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LASER = Light Amplification by Stimulated Emission of Radiation\n\n     Well, let me try to explain this a little more fully.  A laser is a more complex light source than most.  It relies on stimulating electrons in atoms to jump to a higher state.  A laser creates a large population inversion (many atoms with excited electron states).  When these electrons return to their original states, they emit certain wavelengths of light.\n\n     Therefore, in a laser, all of the light is organized and has the same wavelength, rather than the randomized light from most light sources (light bulbs, etc.).  In the laser, there is also a pair of mirrors that causes this light to reflect back and forth, stimulating more electrons in the process.  One of these mirrors is only semi-silvered, so some light can escape from this chamber.  This escaping light is the laser.
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A laser (from the acronym Light Amplification by Stimulated Emission of Radiation) is an optical source that emits photons in a coherent beam. Laser light is typically near-monochromatic, i.e. consisting of a single wavelength or color, and emitted in a narrow beam. This is in contrast to common light sources, such as the incandescent light bulb, which emit incoherent photons in almost all directions, usually over a wide spectrum of wavelengths.\n\nhttp://en.wikipedia.org/wiki/Laser\nhttp://www.howstuffworks.com/laser.htm