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It ain't necessarily so. Some large telescopes are using silver coatings. For example the Gemini telescopes (Boccas et al. 2006). The reason for going with silver rather than aluminium is a slightly improved reflectivity in the near- and mid-infrared (99.1 per cent at 10 microns), but also that the emissivity of the silver coating is around 38% that of ...


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The Poynting vector is useful not because we say so, but because of Poynting's theorem, which in essence states that the Poynting vector can usefully model how electromagnetic energy is moved around a system of changing electromagnetic fields. More precisely, you can define a quantity $$ u=\frac12\left(\varepsilon_0\mathbf E^2+\frac1{\mu_0}\mathbf ...


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Short answer: Yes Slightly longer answer: If you scatter the wavefunction of a propagating electron from a potential (surface of a material for example), it generally splits into two parts - a transmitted part and a reflected part. As the names indicate, the reflected part represents a 'reflected' electron, the transmitted part a transmitted one. However, ...


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First off, I assume you accept that the probability density for the position of a particle is $|\psi(x)|^2$. Now, what roughly happens in real scattering is that a particle whose wavefunction looks like the below image comes in: Then, after interacting with a potential, two smaller packets come out. The packet that transmitted through to the other side ...


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Mirrors flip in the dimension looking into/out of the mirror, not in the others. What changes left/right is what we present to the mirror. If you stand in front of another person, their right is on your left and vice versa, but their top is your top and their bottom is your bottom. That's not the mirror, that's convention for left/right. If you stand ...


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I wonder why Poynting vector can be used to describe the intensity of standing EM wave. It's because a standing wave isn't really standing. Hence the photon in the cavity is off like a shot when you "open the box". It didn't accelerate from zero to c in an instant, it was always propagating at c. The Poynting vector denotes the wave motion even when it ...


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The standing wave solution you quote is a solution to Maxwell's equations - as is any linear superposition of travelling waves. The relationship that $E = cB$ is really only applicable to travelling transverse electromagnetic waves in vacuum, however I note that in this case $E_0 = cB_0$. The Poynting vector (in vacuum) is defined by $$ S = \frac{\vec{E} ...


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About radiation force in a waveguide: Group velocity conveys energy, momentum and information in a waveguide. Phase velocity is superluminal in a waveguide. See for example "Phase, Group, and Signal Velocity" about the case of a waveguide: A waveguide imposes a "cutoff frequency" $\omega_0$ on any propagating electromagnetic waves based on the ...


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From the interior, a spherical mirror can be analyzed as a continuous assemblage of concave mirrors. If you were illuminated by an invisible light source, your image would be reflected from all points on the interior surface according to the mirror equation for concave spherical mirrors: (1/object distance) + (1/image distance) = (1/focal length) The ...


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From what I gather you are describing a mirror that is built like light -> | glass | metal And your question is, why the glass is polished on the outer side? To suppress unwanted reflections/scattering of the light. If you have rough or textured surface you cannot look through it unhindered and will have additional reflections. This is how your brain is ...


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Would you dig a ditch with a surgeons scalpel? Yes, quantum mechanics ultimately underlies all physical observations but the mathematical expressions for large dimensions with respect to $\hbar$ become cumbersome and are replaced by the simplest ones for the appropriate study. Thermodynamics, for the study of bulk matter, blends smoothly with quantum ...


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The billiard balls do not have atmosphere (O2,H2O, N2, CO2, O3, particulate, ...), clouds, forests, terrain, sea. Each component modulate the answer in relation to absorption, refraction and reflection, trapping/reflecting more or less radiation. More heat from the sun at the surface >> more water vapor in the atmosphere >> more clouds >> more albedo ...


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The fact that the ocean is proportionally smooth doesn't matter -- when a light wave with wavelength ~500 nm hits the ocean, all it knows is that it's running into huge, 60 foot tall irregularities. It doesn't care if these waves are small compared to the rest of the earth. I mean, how would it even know? For specular reflection, you need absolute ...


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Gray is not a color - it is a shade. A shade of white. We perceive something as gray when it has no obvious "color" (that is, the amount of red, green, blue stimulus that the cones in our retina receive are roughly the same), and Something else in our field of view is brighter Our eyes adjust our perception of gray or white relative to "something else". ...


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The moon appears white from the Earth for two reasons. The first is that the reflected spectrum of sunlight is very broad and contains no very significant features. On this basis, the spectrum of the moon could be considered pinkish, as the reflectance of sunlight (which appears almost white to the human eye) is twice as effective at red wavelengths than ...


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It is not white, see this link for photos: http://www.mikeoates.org/mas/projects/mooncolour/intro.htm See also this image I took, it does not appear white, one of the seas looks blue. See this photo with increased saturation. It appears that on average the Moon is grey with light coloration aligned with the terrain ranging from yellow to blue. The ...


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The moon is actually grey. You can see this if you look at images taken in space, or, preferably, on the moon itself. For example, this one, of Buzz Aldrin: (Courtesy of NASA) But, seeing as how at night you compare it to a black sky, it appears white.


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For emphasis: The Moon is grey, but it looks white because of scattering along with sunlight. The dark parts - which are less common - are maria, plains of volcanic rock (basalt). They are relatively old, as there has been no recent volcanic activity on the Moon. Most are on the near side of the Moon. By contrast, the white parts are often referred to as ...


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In fact ice is slightly less reflective than water. The reflectivity is related to the refractive index (in a rather complicated way) and the refractive index of ice is 1.31 while the refractive index of water is 1.33. The slightly lower refractive index of ice will cause a slightly lower reflectivity. In both cases the reflectivity is about 0.05 i.e. at an ...


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You're confused about the question, I'm not going to give you the answer. I'll just give you some clues. Clues: 1. Acute angle is any angle less than 90 Degree ignoring Negative value. ( 0 < Theta < 90 ) 2. Retracing means the "Output Light" goes back to the point of "Input Light" and is parallel to each other. Characteristics of the Image ...


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I am here because of the bright spots on Ceres. It does not have the dense atmosphere of the Ionsphere, so I will quote you a reference on the phenomena of Reflection. This is covered by Philip M. Morse "Chpt 7 Hndbk of Physics Vibrations of Elastic Bodies; Wave propagation in Elastic Solids Sec 4. Reflection from a Plane Interface, Surface Waves" '(if the ...


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The issue may be one of purity at the surface of reflection. Silver oxide is black. The presence of black silver oxide on the surface together with un-oxidized silver may be leading to an overall gray appearance. The way to test this hypothesis is to prepare a pure sample of silver in an inert atmosphere, and another sample in an oxygen atmosphere, both ...



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