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Sensei

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Everything posted by Sensei

  1. Plane of incidence doesn't exist as real thing. It's just mathematic tool to illustrate one of many ways photons can be reflected from material. Smooth surface like water (in closed room, where air can't influence it much) or flat glass has all normal vectors pointing in the same direction. Rough surface will have normal vectors disturbed, resulting in disturbed reflections (therefor in 3d applications attributes are called "bump map" and "roughness"). If you have patience watch this 10 min video, how you can manually disturb normal vectors to get disturbed reflections (by adding randomized vector to surface normal vector and then normalize vector): https://www.youtube.com/watch?v=nP425jM1oGM Read more about subsurface scattering http://en.wikipedia.org/wiki/Subsurface_scattering If you will place your hand between strong light source and your eyes, you can see photons passing through your fingers (where body is the thinnest). Modern 3d movies uses subsurface scattering all the time, and 3d games also start using this effect, because it's giving a lot of realism. Here is quite extreme example: On the left girl without subsurface scattering, on the right with subsurface scattering: Subsurface scattering can be quickly described as multi-bounce of photons through different layers of material after refraction, causing whole material to be brighter as a whole. Exiting refracted photons from material are exhibiting internal of material (like veins, bones, internal damages, internal color (f.e. multiple times painted car but with different colors)).
  2. I loaded his xls to OpenOffice.. It has 1300 rows.. >50 columns each Taking screen-shot would be challenge itself (maybe rather hundred screen-shots).
  3. And unlike solid planets, Sun equator rotates at different speed than other regions.
  4. Search for "rats" in this article: http://en.wikipedia.org/wiki/Heavy_water Section "Effect on animals" I noticed something interesting: "An early experiment[10] reported not the "slightest difference" in taste between ordinary and heavy water; on the other hand, rats given a choice between distilled normal water and heavy water were able to avoid the heavy water based on smell, and it may be possible that it has a different taste.[11]"
  5. Are you asking about horizontal line? It's surface of material. On top there is material with refraction index 1.0 like vacuum or (almost) air, on bottom there is material with higher refraction index. Photons are emitted in the all directions, isotropic emission. The one that travel up and left/right are never colliding with bottom material. Those that are colliding with material, pass through it (it's transparent). And perhaps are partially absorbed by medium (not showed). Dashed line is showing example path of such photon.
  6. rasen58, think what really happens there at quantum scale. When electron passes through conductor (that's not superconductor), it's hitting nucleus of material and slowing down. And material is heated. This effect can be even used to cook water for tea or coffee in heating element. Any conductor, any wire, especially resistor, behaves like that. At small voltages, small current, they don't heat to level detectable by human hand. But try to connect plain wire to battery 5 V + and - and keep it in hand, it'll pass current approximately 2.4 A, and in second heat to level you won't be able to keep it in hand. Once electron gave its energy to material, it's lost energy (f.e. it can't be used anymore to produce photons by light bulb). And it's issue in large electronic facilities, like computer server room, either because of money and heat that has to be get rid of (otherwise danger of fire).
  7. Mouse or rats die after week of drinking heavy water. Heavy water D2O, HDO, have just one or two neutrons in Hydrogen more than normal not harmful water..
  8. You should be aware that refraction index is not constant. It's variable depending on frequency of photon. We can even change refraction index for given material on the fly. It's called Kerr's effect http://en.wikipedia.org/wiki/Kerr_effect This can be used to create windows that are transparent or opaque when we need it. Other worth reading things if you didn't already are: http://en.wikipedia.org/wiki/Magneto-optic_Kerr_effect http://en.wikipedia.org/wiki/Faraday_effect
  9. Sensei

    AC/DC Components

    Imagine two roads: 1. cars can travel just in one direction. Speed of all cars is pretty much constant. 2. cars can travel half of time in one direction, then another half of time in opposite direction. Speed of cars is constantly changing using sin(2*PI*frequency*t) function. For 230 VAC with 50 Hz frequency, 1/100 s = 0.01s electrons flow in one direction, yet another 0.01s electrons flow in opposite direction. I made OpenOffice spreadsheet for you: 2 Hz AC result (it's using sin(2*PI*frequency*t)) 5 Hz AC result (it's using sin(2*PI*frequency*t)) When you will pass AC through rectifying bridge or 4 rectifying diodes, 2 Hz AC will change to this (it's using abs(sin(2*PI*frequency*t))): When you will pass AC through 1 rectifying diode, 2 Hz AC will change to this (it's using max(sin(2*PI*frequency*t)),0): I have attached OpenOffice documents in ZIP archive, so you can play with it by yourself. Small frequency is used to better visualize effect. In real rectifying AC->DC there is also rectifying electrolytic capacitor(s) needed after diodes/bridge. So instead of "bumps" like on two last screen-shots, there is smooth flat line of Voltage (pretty much constant velocity of electrons in just one direction). ac 2 hz.zip ac 5 hz.zip dc 2 hz.zip dc 2 hz 1 rectifying diode.zip
  10. At one frequency range material can be transparent, and on other frequency range same material can be opaque. In one episode of Mythbusters they were testing IR camera and experimenting with different materials - which one causes to be invisible in IR camera view. Glass was pretty good at hiding to IR camera. https://www.youtube.com/watch?v=BIHpsyuyV4I Glass testing at ~8 min of video.
  11. Rather because you are greedy, and want software to do work for you for free, instead of letting people earn some money.
  12. You got negative (not from me), because you want to abuse websites that try to fight with guys like you. And you are asking us for helping you abusing their systems on our forum... Whatever you will do, it will be just temporary. They can change font that's rendering texts and distortions within couple minutes.
  13. I have never saw any bit of math in your posts.. Just pure text. Can you please show me your calculations of anything?
  14. You seems to be mixing everything totally.. Misunderstanding even simple things.. I have made animation of how inverse-square law works with any particles. If we have initial 266 particles at center (that's quantity used in below anim gif), and then they are moving in the all directions from center (isotropic emission), the further they are from center, the less particles per area unit. After 1 second, there is still the same quantity of them total. Simply they are spread further each other. Frequency, wavelength, energy and momentum of particle remain the SAME during isotropic emission in the all directions uniformly. Knowing total energy of Sun photons at surface of Earth 1367 W/m^2 (without loses caused by atmosphere) and distance from source ~150 mln km we can calculate energy that Sun (or other light source) emitted in the all direction. 4*PI*r^2 - area of sphere. Replace r by 150 mln km. 2.827*10^23 m^2 area Total energy of all photons of Sun is therefore 1367*2.827*10^23 m^2 = 3.865*10^26 W = 3.865*10^26 Joules per second. With average photon wavelength 532 nm (thus energy 3.74e-19 J ) there is approximately 1.03345*10^45 photons emitted per second in the all direction from Sun surface. Speed of light 299792458 meters per second is experimental data. I don't know about what exponents you're talking about..
  15. What?! Speed of light is 299792458 m/s. If somebody doesn't remember right, he is using 3*10^8 m/s instead. Of course reflection from mirror is from the past. 3.33 ns ago, if you look at mirror from 0.5m. Read more how they emit light here http://en.wikipedia.org/wiki/Anglerfish
  16. Of course it has sense.. Are you talking about spreading photons in the all directions? If you have light source with 1 Watt, emitting photons at 532 nm wavelength, each with E=h*c/532nm=3.74e-19 J in uniform direction like laser. You have 1 J/3.74e-19 J = 2.67*10^20 photons emitted per second. If these photons will hit wall, they are spread in the all directions. Laser "dot" is visible regardless of angle you will look at wall (except behind). Now, the further you're from it, the less photons will reach you, because of inverse-square law. And the smaller intensity your eye will record. Similar multi-bounce of photons happens with Sun light. We can be inside of room, inside of house, and still have pretty bright even though we don't see direct rays from Sun. No. Viewing frustum is method of projecting 3d coordinate to 2d coordinate space of viewing monitor screen.. http://en.wikipedia.org/wiki/Viewing_frustum Ray-tracing engine don't need 3d->2d projection at all. It's sending rays in the all directions to check whether ray hit some geometry or not. From that have information about distance and position of surface that has been hit. And can perform shading calculation of that spot. 3d games demanding speed are doing 3d->2d projection (multiplication of vector by projection matrix), then drawing triangles in reverse order (sorted by z-depth). It's quick and cheap. But in 3d real-time game you won't see mirror of yourself, unless authors cheated with reflective surfaces (it's done by using pixel-shaders usually). In 3d games and 3d rendering engines after transformations camera is always at 0,0,0. Center of everything. But what question? I have no idea what do you mean by "believing in virtual reality"... Does it need "believing in"? We usually stare to mirror from 0.5m or so, so we see ourself that we were 3.33 nanoseconds ago (0.5m distance from us to mirror, and yet another 0.5m back = 1m/299792458 m/s = 3.33*10^-9 s)..
  17. Alive body of animal is emitting photons at frequency ranges below visible spectrum (so they can be visible by IR cameras used by f.e. soldiers). (but it's mostly animals that have temperature higher than environment such as mammals or birds). Except very few animals that emit their own light at visible range like fishes at bottom of oceans. f.e. http://images.nationalgeographic.com/wpf/media-live/photos/000/002/cache/angler-fish_222_600x450.jpg When we see ourself in mirrors we see photons emitted by Sun or light bulbs or LEDs.
  18. Do you have mirror? Do you have laser pointer? Play a bit with it.. You will see where "dot" of laser is ending up. Then read about Snell's law. http://en.wikipedia.org/wiki/Snell%27s_law You should also ask question how is it possible that when we have computer 3d rendering engine, and mirror like surface, when we will look at that surface from right angle we will see our own virtual camera in it (or even camera in mirror in camera in mirror and camera in mirror etc.).. It's called recursive ray-tracing. http://en.wikipedia.org/wiki/Ray_tracing_%28graphics%29 For 1920x1080 with anti-aliasing 4 there is needed to trace 8.3 millions paths of photons per frame. So for 30 fps there would be needed ~250 millions per second. If it works in 3d simulation, why it wouldn't work in real world?
  19. Is product A burned? If so, oxygen is taken from air.
  20. Who exactly? Names.. I don't know any. Theoretical consideration is not the same as "believing in". Scientists generally don't "believe". We use scientific methods and analyzing set of repeatable data to create physical laws describing observations.
  21. Simple solution is not using bind_result() when number of columns is unknown at code writing time, and rely only on get_result() and fetch_array() and problem is gone. This can be nicely packed up in OOP method taking call-back as parameter. Call call-back for each row with $row as param. Internal implementation will be not revealed to using it code. $stmt->execute(); $result = $stmt->get_result(); while ($row = $result->fetch_array(MYSQLI_NUM)) { call_user_func( $func, $row ); } They are almost always available to users from the net - after all you can use MySQLadmin from home, isn't? It might not be the case only in really large companies having everything, all kind of servers. I can write PHP code (and run at mine home PHP server, not accessible to anybody else), which is connecting to MySQL with bought by me external server at servage.net. So it's for sure available from the net. In mine case it's domain like mysql[number].servage.net. Now if some intruder would get between mine machine and ISP (intercept wifi *)? intercept provider?), and make fake DNS (simplest one code that I wrote in C/C++ in couple minutes is working like proxy server, listening for packets at 53 port, then logging stuff to file, and passing to some real DNS server, and returning answers to caller. After some time they learn what domains machine is asking. Can prepare fake HTTP(S), fake MySQLdb, fake FTP - check for f.e. "mysql1099.servage.net" and instead of returning true IP, return their own IP where is custom made server. If they will be transparent - pass everything to real one, without any modifications, and vice versa, such server can be unnoticed for months or years by anybody. *) mine ex- neighbour was uploading code to Linux-based Wifi router (typical one router for 50$), and executing his code on it.
  22. If DNS were intercepted, and SQL database is external (different domain than PHP server; everything that's not 'localhost'), PHP code asking for connection to database might try to connect to SQL that's fake. Field names, databases, tables might be all fake. If fake database will have weird column names with string '); [....code to execute...]' hacker will intercept also PHP server (if PHP executable/SQL modules don't do special checks for verifications of database field names obtained from SQL from net).
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