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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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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What type, and how strong a spotlight will I need? [closed]

So I'm working on a photography project in which I cannot use a flash, but rather, I need an intense beam, which will provide 1 1/2 X's the brightness of full sun (noon, at the equator) > however, ...
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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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How to make light resonance? Is this a proof that c is not constant in lasers? [closed]

How to make light resonance? I know that it's possible to amplify electromagnetic waves e.g. $$LCR \ \ \ \ f_0 =\frac{1}{2 \pi \sqrt{LC}}$$ but how about light resonance? $$A*f=\frac{c}{2\pi} $$ Btw ...
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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!

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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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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How to explain why an element constantly absorbs certain wavelength of a starlight? [duplicate]

I really cannot grasp what happens to starlight that gets absorbed by an element or more. The atoms should have a capacity and in no way constantly absorb light like a sink. If that light is somehow ...
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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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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
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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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How does the combination of lens create a sharper image?

There's a line in a book which states that the combination of lens helps create a sharper image, but I don't understand how. Does more magnification mean sharper image?
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What happens to the time period when refraction occurs? [duplicate]

I was studying light and had a doubt that when refraction occurs (rarer to denser just assuming) then frequency remains same but lambda (wavelength) and velocity decrease. But I cant quite figure out ...
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Why do lightbulbs produce any light, when the light they produce is incoherent? [duplicate]

First let's talk about lasers. A simple three level laser produces coherent light from stimulated emission, and incoherent light from unstimulated emission. I have been told that the intensity of ...
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Mutual gravitational acceleration (or deflection) of light beams as a function of the angle between them

Given Einstein's famous equivalence between energy and mass, $E=mc^2$, a light beam with power, $P$, has an energy per unit length of $P/c$ and an equivalent mass per unit length of $P/c^3$. A short ...
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Is it possible to visualise red shift?

If a picture of a star or galaxy hurtling away from Earth is taken, does it appear red despite it being a different colour? Would a blue coloured star moving away from us appear red to us or vice ...
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Why is light not a longitudinal wave?

Here is a typical representation of light waves using wavefronts. In the diagram it depicts the peak as the lines and the throughs as the space half way between consecutive lines. Considering light as ...
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How many oscillating fields exist in a light wave?

Is light made from one magnetic and one electric field which are oscillating perpendicular to each other? In textbooks, it says that the light can be seen to oscillate in every plane perpendicular to ...
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Alternate sky colors?

Ok, so the sky is blue because of Rayleigh scattering - blue wavelengths of light scatter off atmospheric particles in the air (more/more easily than others) - I understand this pretty well. So, if ...
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