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You ask: Do atoms of a surface excite to reflect the light? but it's actually the other way round. Reflection occurs because the oscillating electric field of the light produces oscillating dipoles in the electrons in the substrate. These oscillating dipoles in turn radiate light isotropically and the reradiated light interferes constructively only in ...


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Short answer: Light is absorbed and re-emitted all the time. Colors and reflectivity all depend on the electrons in the material, and what the material is. Sometimes photons are converted to heat in a material. Other times photons pass through a material or are re-emitted (so it may look like they just "passed through"). Depending on what photons are ...


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Light of different color is understood as a wave of different frequency of oscillation. Matter in surfaces has characteristic behaviour for each of these frequencies, based on its chemical composition: electrons in the surface oscillate and absorb a lot of light when its frequency is around one of resonance frequencies of the matter; and the electrons ...


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The angle of the first diffracted beam (assuming we are talking about double slit, and not worrying about the width of the single slit) is $$\alpha=\frac{\lambda}{d}$$ Then we find the distance from $$\frac{spacing}{distance}=\alpha$$ So $$distance = spacing \frac{d}{\lambda}=1.5cm\frac{30\mu}{500nm}=0.9m$$ Diagram:


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In my answer to this question: (What is the sun's spectral series?), I give a very detailed answer about why mixing colours of light produces other colours and how it is purely a result of biology and evolution. I also delve a bit into the structure of the human eye and why, in fact, only three colours are necessary to reproduce all of the colours we can ...


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A "normal, healthy" human eye has two types of light-sensitive cells in the retina: rods ("color blind", but capable of sensing low light levels) and cones: cells that are sensitive to different bands. See this figure for their relative sensitivity (from http://hyperphysics.phy-astr.gsu.edu/hbase/vision/colcon.html) When you look at a spectrum of light, ...


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The cells in our retina that detect by frequency (read: colour) detect most strongly in three slightly different bands we know as Red, Green and Blue. To make a slight correction I would say an incadescent bulb is quite far from white, so I would rather proceed talking about sunlight on a clear day. The reason why sunlight appears as white as say a white ...


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Take a look at this picture - and ask yourself why the operator of the camera has the cloth over his head (the cloth is black on the inside) as he is looking at the back of his camera - which has a piece of ground glass where the image from his pinhole camera is forming: This used to be how photography was done: Align the camera to the subject, focus (if ...


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From http://pixsylated.com/blog/canon-speedlite-optical-wireless-fundamentals/ : With optical wireless, the master sends instructions to the slave(s) via a series of pre-flashes that come just before the main flash. These instructions tell the slave what mode to use (ETTL, Manual, or Multi), what power to fire at, and what sync speed to use. ...


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From what I read here: http://scantips.com/lights/awl.html, the master flash uses IRlight to control the other flashes (just like a TV remote control), not visible light. (The red thing is the IR sensor) Anyway, light can transmit information just as any electromagnetic wave. Otherwise, you wouldn't be able to see the objects around you! There would be ...


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The two lights cover different areas of the drivers view. If there are other cars near, it's important do not aim the light to the eyes of other drivers (or their mirrors). But Also, it's important to cover as much of the street ahead as possible. One bulb, together with the surrounding reflector of very specific shape, aims the light to the street up to a ...


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I am just guessing on this based on the reference you posted in the comments. Sometimes dB's are referenced to a max level, like with audio at 120dB. In this case they look at the difference between the maximum. In your case, 10,000 is the max, or 40 dB. Based on this scale comparison: I would guess apostilibs to dB is done like this: $dB = 40 - ...


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The failure of Michelson-Morley experiment does not imply that aether does not exist. It only implies that we cannot detect it. What if space-time is 'saturated' with so many 'beams'of light that the light waves themselves are there own medium. Is this valid? This is incorrect. A medium is sought to be something material. If saturated light is the ...


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Are there experiments that could show that light waves resemble more say square waves than sine waves? Are there experiments that could show that light waves resemble more say square waves than sine waves? Temporarily looking at your example of a square wave, a square wave of spatial wavenumber $k$ can be represented in a Fourier expansion as a ...


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So, my best understanding: The basic solution to the wave equation is $$\Psi(x,t)=Ae^{ikx-i\omega t}$$ Where the signs are arbitrary. If you combine this with the good old Euler Formula this expands to $$\Psi(x,t)=A\cos(kx-\omega t)+B\sin(kx-\omega t)$$ Where the imaginary part is absorbed into that B


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This is due to a psychological effect known as Color constancy. Your brain seems to see something based on the context around it, for instance the blue image projected on the red wall may be more black than blue but your brain will compensate for some of that because you also see the red wall. This is also the source of a number of related optical ...


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Black holes have light not escape them Beacuse. A black hole has so much mass and gravity can't escape it, not even light! The fastest thing in the universe!


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In an acceleratingly expanding universe, there will be an emission time of light from a distant galaxy after which we can never recieve newly emitted light. Old light will eternally be received, but even more dimmer and red shifted. See The Long–Term Future of Extragalactic Astronomy for more information.


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Just think about it a little in terms of light rays and reflecting surfaces (mirrors). The light rays from the right hand of the driver behind you are reflected by the mirror to reach your eyes on the right of the light rays from his left hand, so you see them that way. Likewise for his head and torso. But if you look straight at him, his right hand appears ...


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The corners of the triangle represent some standard definition of red, green, and blue. There's no particular reason that they should correspond to single wavelengths, although admittedly the closer the standard colors are to the single-frequency curve, the larger the visible gamut would be. The standard colors were undoubtedly chosen as a compromise based ...


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The magnetic field polarizes orthogonal to the electric field in free space. We generally only talk about the electric field because Maxwell's equations define a one to one relationship between the two. It would make just as much sense to only talk about the magnetic field. We choose the electric field because, in general, when light interacts with matter ...


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The magnetic field does not vanish when light is polarized. A changing electric field induces a magnetic field, and a changing magnetic field induces an electric field. This is why, in the propagation of an electromagnetic wave, there is always an oscillating electric field coupled with a magnetic field oscillating perpendicular to this electric field. You ...


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It's 100% just coincidence. There's no plausible way in which these two facts could possibly be causally related. The temperature of the Sun isn't in any way influenced by the transmission spectrum of water, since water molecules do not exist inside the Sun (it's too hot for them to be stable); and, vice versa, the transmission spectrum of water could ...


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Perhaps I can piece all these thoughts together. Black bodies peak at a variety of wavelengths. And our sun's evolution is expected to wander in temperature as simulated here: And during its aging there has been times when water and the radiation have not lined up. Perhaps we are here now partly because the characteristics of our environment now (wet ...


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Surface coating of an integrating sphere is optimized for low losses. This white coating (barium sulfate or PTFE) acts like an ideal lambertian scatterer. all light is scattered (Ok, not 100%, but a very high percentage like 99,5%. See ressources) it is emitted in the hemisphere following the cosine law: perpendicular to the surface it's highest. ...


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In a sphere, any light emitted from the center will reflect off the sides at normal incidence come back to the center. In a cube, some rays never return to the center, so you aren't measuring all of the light emitted, which defeats the purpose of the device.


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electromagnetism is not a handed force. So i don't think you even need to use vectors that are transverse. I recently, learned about a mathematical object called a differential form. a dx+dy is like the k unit vector and dx-dy is like -k. So spin can be described in a more natural way that does not resort to a perpendicular direction. Definetly, more than ...


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light rays are not one dimensional objects. True, in the figures that directed segments are shown. Mathematically, you can think of sort of an infinitesimal vector showing that direction. it can be made infinitely small. is that 0 dimensional small, i don't know. I don't think it is. It would have the dimension of dx.


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You are right that the oscillations of the electromagnetic field need not have any spatial extent. The oscillations, as you point out, are in the strength of the electric and magnetic fields. If I understand your question correctly, you are asking why then can some objects distinguish between the two different polarizations of light. This is because ...


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If instead of the string Light were to be used then it will pass through both of the slits S1 and S2. The book is using this analogy to explain the concept of polaroids. The whole string-slit system that your book quotes is analogus to the above shown light-polaroid system. Light will not pass through the second polaroid. I am not explaining how polaroid ...


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so what if a light beam was pointed somewhere behind the event horizon to the outside, Inside the horizon, the curvature of spacetime is such that the direction "to the outside" is the past time direction. In other words, to go 'back' towards the horizon is as impossible as it is to go 'back' in time. Indeed, for the same reason that we inexorably ...


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Here is some information adapted from the definitions found in Schott's 2013 Optical filters Catalog: [For all the wavelengths of the visible spectrum,] The spectral transmittance is the ratio of the transmitted [exiting] (energetic) spectral flux to the incident [incoming] (energetic) spectral flux. [of the illumination seen through the filter]


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A good question for anyone who has thought about the big bang,red shift and Hubble etc. There are valid questions to be raised concerning Hubble's red shift leading to the big bang theory. Firstly, space is commonly regarded as a vacuum but this is not the case. Space contains a variety of matter ranging from atoms, to molecules, gases and solids and myriad ...


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The most elegant way I've seen to describe this is described in the paper The river model of black holes. If we write the Schwarzschild metric in Gullstrand-Painlevé coordinates we get (in units where $c = G = 1$): $$ ds^2 = -dt_{ff}^2 + \left(dr + \beta dt_{ff} \right)^2 + r^2 d\Omega^2 $$ where: $$ \beta = \frac{2M}{r} $$ This looks like the Minkowski ...


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General relativity describes gravity as the curvature of space-time. So to understand how black holes work, we must have a basic idea of how space-time works. In regular 3D space, the length $\Delta s$ between two points is $\Delta s^2 = \Delta x^2 + \Delta y^2 + \Delta z^2$. This is just the pythagorean theorem applied in 3D. But in space-time, where we ...


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As you said, since nothing can go out from the event horizon, if light is sent from within the event horizon it does not escape. However, it is not true, that light will slow down and go back. In fact, inside the event horizon all accessible paths point towards the center of the Black Hole. This means, that, once inside a Black Hole, you will be pushed ...


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Irrespective of where the light comes from, your eye judges the colour of light by the way it stimulates the three types of cone cell. The cone cells have broad and overlapping spectral responses: (picture from the Wikipedia article I've linked) but to a reasonable approximation you can think of the three types of cone cell as responding to red, green and ...


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There is no real image on the mirror surface. Infinitely many rays arrive to every point of the mirror surface and infinitely many rays reflect from every point of the surface. For example CCD sensor is a polished flat surface that does reflect some amount of light, so if it is exposed (without any optics) it can be considered a kind of a mirror - see here a ...


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Yes, there are infinitely many rays radiating from a single point, but only one of them reaches the eye. Try drawing up a picture of the light rays reflecting off a mirror. For each point that gives off light rays, only one of them reach each eye.


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You can actually observe barometric light if you have access to one of those old pen-style mercury arc lamps. Turn it on, let it run for 5 minutes (and wear the necessary eye protection), and then turn it off. Then, in a dark room, rub the hot glass tube up and down with a piece of cloth. You will observe flashes of purple light as you run your hand up and ...


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To answer this question we also need to know why some things are not transparent and why certain things, water for example, don't behave in this way. A substance's interaction with light is all about interactions between photons and atomic/molecular electrons. Sometimes a photon is absorbed, the absorber lingers a fantasctically short while in an excited ...


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Nothing in the universe is continuous. Matter and light are made up of particles, and physicists have strong reason to believe that even space is quantised. As for the mirror, photons travel from the lightsource to the object. There they are either absorbed or reflected, depending on their wavelength and the properties of the object at the point of ...


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The approximate number of photons which strike a mirror and enter your eye over the period of a couple seconds is a massive quantity (in Mathematica): << PhysicalConstants` Convert[(1 Milli Joule 600 Nano Meter)/(PlanckConstant SpeedOfLight), 1] Output: 3.02047*10^15 Since this is in the quadrillions, for all practical intents and purposes, ...


0

A Mirror flips the image front to back, not left to right. In the mirror your nose is in front of your face, but in reality it should be behind your face. Because your image is flipped front-to back it just so happens to appear from our common sense perspective that left and right are actually flipped. The L-R flip is an illusion symptomatic of the front to ...


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Will this "oldest light in the universe" ever completely cease to exist, or does light stay around indefinitely. Light at the micro level is composed out of photons, the elementary particles of light . In addition to reflections light/photons undergo absorptions when hitting/interacting with matter. Photons can be completely absorbed or change in energy ...


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Light is basically just a stream of Photons. I think Photons can cease to exist because when they are absorbed, it's the energy of the quanta that is absorbed. The Photon itself does not exist anymore, Photons can only exist when travelling at $c$. The re-emission means that the Photon is produced again, it's not the same Photon which was absorbed earlier.


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No they cannot decay. Even if they were unstable, just because they are traveling at c time dilation makes it so that for a photon in any reference frame time t = 0, so they cannot possibly decay. Edit: It can be absorbed and re-emitted, I guess in that sense, it "ceases to exist" for some time.


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A detector generally provides values that are proportional to the power spectral density (PSD) of the radiation hitting it. Energy per time interval (collection time), per spectral interval (pass band, slit width, pixel width, ...). The Fourier transform of the PSD is the time-domain autocorrelation function of the radiation. The autocorrelation function ...


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Presumably you have measured your spectrum as a function of wavelength, so you have $\mathscr{F}(\lambda)$, which is an power per unit wavelength. You must now convert this power per unit frequency spectrum. So we seek $\mathscr{G}(f)$ where $\mathscr{G}(f)\,|df| = \mathscr{F}(\lambda)\,|d\lambda|$; given $c = f\,\lambda$ we have: $$d\lambda = ...


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Electronic energy levels are quantized. The bigger the box the electrons can move in the smaller the energy needed for a transition. H2O only contains 3 atoms (and small ones at that) so the box is small and the transitions are in the UV. The same goes for O2, CO2.



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