# Tag Info

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From the wiki article on color vision as an illustration of how photons are absorbed: Perception of color begins with specialized retinal cells containing pigments with different spectral sensitivities, known as cone cells. In humans, there are three types of cones sensitive to three different spectra, resulting in trichromatic color vision. Each ...

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Photons can be created and destroyed freely, since they don't have charge or mass. Turn on a light, and you create many photons. Any body (made of atoms) not at absolute zero temperature will spontaneously emit photons. They are consumed just as easily. Most any bit of bulk matter will absorb a photon in the electrons on the surface, transforming the energy ...

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The distance between the two is assumed to be constant. However, when you look at an object that is far away, it "seems smaller". What that means mathematically is that the angle from one end to the other, as seen at your eye, is smaller. Now you can't tell the difference between something that is "small and close", and something that is "big and far". So ...

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Light from all over the place hits your eyeball fairly randomly. The lens forces light from a specific angle to hit a specific part of the retina. This HowStuffWorks article shows how the mechanics of that work. The only major differences between camera lenses and eyeball lenses is that we can dynamically alter the shape of the lens to focus on different ...

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Imagine a spring-loaded trap with a hole that's sized such that only a particular size of object can enter the hole and trigger the trap. The molecules involved in vision are like that trap, with a bond having an electron energy gap tuned to the visible frequencies of light, encapsulated in a specialized protein that transforms the absorbed energy into a ...

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Possibly some semantic confusion here. Glass, with a simple refractive index, does not "absorb" light, it is transparent. Therefore the amount of light that emerges on the other side, for a given angle of incidence, is independent of the thickness of the glass. Instead, some of the incident light is reflected from the first boundary as the light enters the ...

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The underlying principle is to use interferometry and the Doppler effect to remotely measure the velocity of a reflecting surface. When a moving object is illuminated with coherent light it reflects it with a wavelength shift proportional to its velocity. This is the well-known Doppler effect. The frequency shift relates to the source's velocity as ...

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The diagram you want to use looks something like this: Depending on how much attenuation there is in the membrane, you need to consider the potential of multiple reflections (or not). I actually analyzed this problem in some depth - considering not only the intensity of reflections on the different surfaces, but also multiple reflections and even the ...

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Keep in mind that your eyes perceive a fixed field of view. That is, you see a certain angle in front of you. They do not see a fixed distance across your line of sight. This means that the farther away for you you look, the more distance there is from one side of your FOV to the other. When you look at parallel railroad tracks that maintain a certain ...

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To add to Rob Jeffries's answer: the absorption data for glass are separate from the refractive index and are measured by measuring the attenuation of light through a known thickness of glass, after taking account for the reflected amounts as described in Rob's answer. Theoretically, the refractive index and the absoption data are united in a complex ...

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Lenses can exhibit chromatic aberration due to a color (wavelength) dependent index of refraction in the lens material. Chromatic aberration can cause the three colors from the red-green-blue (RGB) display to separate when viewed off the lens axis: Left: on axis. Right: off axis. In less pronounced cases, this might lead to a ghosting of images. ...

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If the slit is much smaller than the wavelength, there will not be significant path-length difference between beams passing through different points inside the slit. If the slit is much larger than the wavelength, most of the beam passing through the slit will not be affected by the edges of the slit. I also guess that Born had in mind Fraunhofer diffraction ...

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There are several options to increase the signal size: 1) increase the length of the path (look at the slab from side to side instead of from the front - you may have seen a "green edge" on a glass coffee table - that's because you see light coming through a much thicker slab of glass) 2) Use multiple sheets of glass on top of each other. Be careful about ...

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Photons are energy. When a photon hits your retina, that energy is absorbed and converted to electrical energy in your optic nerve.

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Although there are already some excellent answers, I believe they are a little complex. Please allow me to offer a simplistic answer. Let me start with the analogy of sound waves and the ear. The sound enters the ear and causes certain cilia to vibrate in response to the frequency and amplitude of the sound wave. Similarly a photon (as a wave), enters the ...

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I'd like to add another take on Cape Code's answer. Holography works because, given reasonable physical assumptions, solutions to the Helmholtz wave equation are uniquely defined by the values of the solutions on one plane. So if we can light a phase / amplitude mask encoding a particular wave equation solution on a plane with a plane wave from a laser, the ...

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Use a sodium lamp positioned above the prism and slightly to the side to create a reflection at the interface. Look for interference patterns at the prism/prism plate interface. If the spacing between dark fringes is small (and you have many fringes), you have a problem. If you have very few fringes and the spacing is large, the interface is close to being ...

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Because of diffraction. When the photographic plate is exposed, it blackens and change its refractive index in a spatially varying manner. When illuminated again by the reference beam it can be considered as an amplitude transmittance. In 2D you would define it as the complex function: $$t(x,y)= T(x,y)e^{i\theta(x,y)}$$ Let's say your reference beam can ...

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Everything is about electromagnetic waves. At the border of medium one of the components of electric field have to be continuus and other component of electric displacement field. Such calculations leads to Fresnel equations

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x-ray diffraction is not caused by atoms absorbing radiation. x-ray diffraction and diffraction by gratings do have an underlying mechanism in common. In both cases, when two incoming rays of waves (x-rays or light waves, in the case of optical diffraction grating) both rays bounce of the crystal or grating, they have travelled a different distance, say ...

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Greatly rewritten based on feedback in comments In order to understand this issue, it is worth considering what a telescope (or any optical / radio imaging system) really does. Taking a simple parabolic mirror, the shape is chosen such that the total path length for all rays "from infinity" to the focal point is the same. By making the path lengths the ...

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Picture yourself looking into a large mirror on the wall. Now picture the mirror is made up of smaller, tiled mirrors. You will still see your reflection. If you begin to remove the tiles, so that there are only a few left, you can still use them to reconstruct the image of your face that was given by the original mirror. This is what is happening with ...

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A sum-frequency system with a "hot" mirror could act something like an optical switch: Unlike a switch, the output frequency will be different from either of the inputs. Edit: For an example of sum-frequency generation crystals see: Thorlabs Introduction To Periodically Poled Lithium Niobate (PPLN) (PDF) Thorlabs also sells hot mirrors.

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Typically the order of magnitude of angular spread of a fringe in a pattern can be given by lambda/Width. If lambda is much smaller than width the diffraction pattern will be difficult to see. In the other case of lambda much greater than the width the entire screen would be covered by just the first fringe.

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