Questions tagged [visible-light]

Questions related to the perception and measurement of light (primarily in the visible range), its mathematical description, the reproduction of colors by different means, color combinations, etc. Please use the tag [electromagnetic-radiation] if you want to refer to the general form of light.

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Did Huygens understand light to be a transverse wave or a longitudinal wave?

We have this source that claims Huygens "assumed light to be longitudinal", which contradicts this source which claims "Huygens believed that light was made up of waves vibrating up and ...
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Why do we draw two rays from a same point on an object during image formation?

When we draw ray diagrams for image formation of an object through refraction or reflection we generally draw two rays emerging from a common point on the given object, by our nature of thinking (or) ...
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WHY DO WE SEE DISTINCT OBJECTS? [migrated]

Could someone help me find the post of the person who wondered why, with all the light rays bouncing off of multiple objects and crossing in complex ways, do we see distinct objects instead of a light ...
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Non-dispersive mediums for light

Apart from the vacuum are there other mediums for which light velocity does not depend on frequency?
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Is it possible to build a camera that takes pictures in different spectra? [closed]

How would you approach the problem of building a camera--a device capable of producing an image--sensitive to some arbitrary part of the spectrum? Radio telescopes are one example of such a device. ...
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Color: when electrons of a certain colored object absorb light, how come it does not remit that color back out? [duplicate]

If an electron absorbs a photon with a specific color of light, shouldn't it reemit that colored photon back out when it falls back to its ground state? For example, I've read that a black colored ...
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Reflection of light on a colorless material. What happens on atomic level?

I try to understand reflection explained with photons that are interacting with molecules on atomic level. For this I would like to start with an example and ask the question based on this: Say I have ...
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Why does the boundary shows different colors between black and white regions on a projector screen?

Original Question: My friend took a picture of his screen from an angle (please see the attached picture) and found that the colors of the boundaries from white to black and ones from black to white ...
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11 answers
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Can you actually stand inside a rainbow? I see people claiming you can

I have been thinking about this for ages and it has been driving me crazy. I was convinced that rainbows are always complete circles that appear to be arcs because they cross the horizon. Then, I saw ...
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Is it possible to get a material which yellow in normal light and doesn't reflect spectral yellow?

Imagine an object which reflects only green and red spectral colors. In normal light, it should appear yellow. But when we light up this object by spectral yellow color, it should appear dark, because ...
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Reflection on a surface: Focused or non-focused? [closed]

For an experiment with my students I want them to measure the reflection of 1x1x1 cm cubes with different surfaces(wood, alu, super black) All studs will have its own little "black box", ...
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Does destructive interference of photons destroy energy? [duplicate]

I am wondering about if two light beams comes in opposite phases exactly against each other, destructive interference will happen. From what I have found on the internet many say that energy is not ...
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Absorption spectrum of white light of the Sun

When some photons in the white light from the sun are absorbed, this means some wavelengths will be missing, so how does that light still appear 'white', although some of its constituents are missing?
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Specular and diffuse reflection at the same time

if we know that tomatoes absorb all the light and reflect the red diffusely, how can we see the reflection of all the light specularly at the shinnig point? there isnt an absorption of other colors at ...
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Extent of scattering of light

I am absolutely no expert in physics but I really want this question answered and the reputation of the forum is good. So my question is if I have a magnifying glass, for example, it can fix the light ...
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How do we define a color? [duplicate]

Is Black a color or just the absence of others colors/light . What actually constituents colors? How do we define if something is a color or not?
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Are radiance and luminance really independent of distance to observer?

Recently, I learned that apparently both radiance and luminance are independent of the distance between the light emitting object and the observer. The reasoning was that although the radiant/...
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How come $P=Fv$ applies to light? [duplicate]

I was asked the following question in a physics worksheet: A $2.0 \,\mathrm{mW}$ laser is shone onto a metal plate. The cross-sectional area of the beam is $4.0\times 10^{-6} \, \mathrm m^2$. Assume ...
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Glass Slab to Prism! [closed]

Hi I want to know how the refraction of light takes place in different cases! Like Here is an image In this case the light refracte simply. While in the prism refraction of light becomes quite tricky....
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Can a convex lens form a real image of a virtual object?

What is a virtual image? How is a real image formed from a virtual object in the case of a convex lens?
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What type of scattering happens in dark field optical microscope?

I know that in dark field optical microscope, the light scatters off the specimen under an angle and falls on the detector. I am curious if the scattering that is taking place there is considered to ...
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Will light follow a stream of water?

I am a deep admirer of natural sciences, and especially physics, but, alas, only at a lay level; so I'll ask forgiveness in advance for my poor terminology and half-baked understanding of the ...
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Antireflection coating: does reflection that destructively interferes lead to more transmitted light?

I was watching some media on how solar cells work, and the description of the antireflective coating confused me. According to this video and this Physics Asylum video, the antireflection coating is ...
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How to achieve uniform gaussian profile? Beam profile has grainy/multimode pattern, EO says it's due to different emissivity of each phosphor atom

I'm required to make a jig that measures the divergence angle of a collimated beam. The setup is straightforward as shown below. The single-mode fiber optic cable, collimator & NIR camera are the ...
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How thick would glass need to be for no light to pass trough?

There are no ideal materials, and even though glass is used for optics due to its low absorption of light, how thick would normal window glass (rough idea for specific material) need to be so that it ...
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Propagation of light in vacuum [duplicate]

Suppose, you and your friend are present in a pitch black, perfect vacuum side by side. Your friend has a flashlight which he flashes in front of him. Will you be able to see/perceive the light or ...
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A (Mostly) True Violet Pigment

Is there a "True Violet" dye or object? That is, one that reflects higher frequency light than blue, but doesn't reflect red light? All the chemical dyes I have found were part violet, part ...
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2 votes
2 answers
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Why do metals appear as coloured in flame tests, while at room temperature they don't?

I'm not sure if this is more of a chemistry-type question, but my question focuses more on light spectroscopy than the chemical elements; Why do some metals appear coloured in flame tests while they ...
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Frequency and Wavelength of light in water [duplicate]

It is known that the speed of light is slower in water than in air. Does the frequency remain constant and on exiting the water, has the frequency changed?
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If the human eye can see green so well, why don't flames and such that emit a broad rangecof wavelengths ever appear green?

Similar questions have been posted many, many times before, but.... If a black body at the correct (average) temperature is 'centered' on the green, and human eyes our retinal cones) see best in the ...
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What does light travel through or why it is independent of a medium? [duplicate]

According to my research and understanding I cant get over the fact that light needs no media to travel, or is it scientifically or mathematically proven?
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How does paint of two color mix to form one of new color?

Suppose I take bit from two paints of different color and I smudge both on the same spot on a piece of paper, I will get a new color. What exactly is the physics behind this?
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Why we consider light as a rectilinear stream of photons and also a wave of photons?

By Young's double slit experiment it was clearly proved that light was not a rectilinear beam of photons an assumption made by Issac Newton. BUT we still consider light to be a straight beam and we ...
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2 votes
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How ample is a wave amplitude?

Is it possible to actually measure/deduce the amplitude of a wave? We know that the length of am infrared wave is a fraction of a millimetre, do you have any idea what is the range of the physical ...
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Snell shortest path : would the path depend on the observer classically?

Fermat principle for deriving Snell's law reads formally as minimizing : $$T=\frac{x}{v_1\sin i}+\frac{L-x}{v_2\sin r}$$ Where $\sin i=\frac{x}{\sqrt{h^2+x^2}}$ is the incidence angle sine and $\sin r=...
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Paradox of light passing through prism and glass slab

When white light passes through a glass slab, Newton's assumption is that a slab is made of 2 glass prisms placed in opposite direction, such that dispersion of both is cancelled out and a white light ...
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3 votes
2 answers
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What exactly is "dense" in Optical Density?

My book states that: When passing from one medium to another, if light slows down, the second medium is said to be optically denser than the first medium, and if light speeds up, then the second ...
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Tangential rainbows?

My kids just made me aware of a rainbow phenomenon I have never heard of before, happening in the sky up above our heads. I have heard of (and seen) double rainbows before, and I was aware that it's ...
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Can we apply lens makers formula when medium on either side of the lens is different?

Lens maker's formula, which is $\frac{1}{f} = ({n_{liquid}{-1}}) [(\frac{1}{R}) - (\frac{-1}{R})]$. Can one apply lens makers formula when medium is different on both sides? If NO, why? Should we use ...
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Why does the fringe pattern of an interference pattern get darker as the anti-nodal lines increase?

Why is it that the constructive interference fringes get darker as the antinodal lines increase? For example the maxima antinodal line:0 is the brightest. Why do they decrease in brightness after that?...
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How do you make light?

We make light making a charge oscillate, or heating a body. Are there differences between the two processes? But, above all, are there other ways in which we can produce em radiation?
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Clarifications about units of Photon Flux (PF) and Photon Flux Density (PFD)

I have an emitting source of light (this LED - Light Emitting Diode, UO variant). On page 5 I read the minimum PF Photon Flux is ...
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Are laser diffuse reflections really so dangerous?

Class IV lasers are lasers with an optical power higher than 500mW, and for these lasers "even diffuse reflections can cause permanent eye damage". Well, I would like to understand how this ...
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The speed of time [closed]

If the speed of light is 14,545.075 x the speed of sound, could the speed of time (and/or gravity) be 'something' like that times the speed of light, say 2,705,384,023.877 m.p.s? (Sonic boom > ...
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4 votes
1 answer
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How can light penetrate gold in an astronaut's visor?

Astronaut visors use a thin gold layer to decrease intensity of IR radiation coming from the sun. The thing is, gold is a conductive surface, so how can it transmit light through it. Is this related ...
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Where/ how does light propagate? [duplicate]

The Michelson–Morley experiment proved there is no aether, but we (used to) know that a wave needs a medium in order to propagate. Einstein showed the invariance of speed but assigned no properties to ...
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Earth colliding into planet-sized object faster than speed of light [duplicate]

Imagine the following scenario: Earth is travelling in one direction at just over half the speed of light Another planet-sized object is traveling in the opposite direction towards Earth, also at ...
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8 votes
2 answers
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Failure of Newton's corpuscular theory and success of photon theory of light

Corpuscular theory of light States that: Light is made up of small discrete particles called "corpuscles" (little particles) which travel in a straight line with a finite velocity. ...
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Do prescribed glasses transmit light? [closed]

If prescribed glasses can transmit light, what percentage of light can it transmit.
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4 answers
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Doubt on photoelectric effect

One failure of wave nature of light in photoelectric effect was that increasing the intensity of light did not increase the kinetic energy of electrons. I don't understand how this is true. We know ...
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