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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Why can't we have a wave of particles?

I understand the nature of light can be complex and has extensive theories/experimental data. We hear light can be both a wave and particle, so why can't it be both, a wave of particles?
15
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3answers
2k views

Why is the bottom part of a candle flame blue?

What’s the explanation behind the bottom part of a candle flame being blue? I googled hard in vain. I read this. I don’t understand how it’s explained by the emission of excited molecular radicals in ...
14
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7answers
9k views

Why does light change direction when it travels through glass?

This was explained to me many years ago, by a physics teacher, with the following analogy: "If someone on the beach wants to reach someone else that is in the water, they will try to travel as much ...
8
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4answers
442 views

How can a body be transparent?

How can a body be transparent? I need the theoretical explanation for the same. Has anybody succeeded in doing that practically?
6
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4answers
1k views

The Sun as a gravitational lens

Since the Sun is a gravitational lens with as focal length of 550 AU for visible light, with an immense amplification factor, shouldn't it light up objects hanging out there? We should get solar ...
5
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5answers
314 views

How is it possible for the wavelength of light to change in a medium?

So my physics class has just finished a long unit on optics while at the same time I've been trying to teach myself relativity. I admit my understanding is probably rudimentary, but I figured all the ...
5
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2answers
234 views

Is a Perfect/Lossless Mirror possible?

In traditional mirrors, some of the input light is absorbed by atoms in the mirrors surface and are 'lost' as heat, degrading the quality of the reflected image. Could this loss be compensated by an ...
5
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2answers
682 views

Which solution to the electromagnetic wave equation is the most accurate model of monochromatic light?

When a photon is modeled as a monochromatic electromagnetic wave its electric and magnetic components are usually taken to be sine waves (for example here ...
3
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1answer
93 views

What are the common points between physical optics and geometric optics? [closed]

I am trying to write a paper about light, I want to discuss the two way of studying light, the physical/wave optics and the geometric/ray optics, but I want to write a general introduction about them, ...
3
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4answers
387 views

How are we able to view an object in a room with bulb..?

This is a very basic question on optics. How are we able to view an object kept in a room with a bulb? From what I understand, light rays from bulb will hit the object and some colour will be ...
20
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4answers
35k views

What do ants see?

After watching some ants in my garden today, and then looking at this very illuminating demonstration, I got to wondering, about what they would see. Not specifically ants (I understand their ...
14
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1answer
400 views

Does my green laser pointer emit three distinct frequencies, or is my measurement flawed?

I was playing around with a cheap diffraction grating and my set of laser pointers, and I noticed that while the red and the blue pointers produce a single point in the spectrum, my green laser ...
14
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3answers
879 views

How would neutron matter appear to the naked eye?

Neutron matter is matter comprised entirely of neutrons, as it exists in neutron stars. Most optical phenomena encountered in everyday life, such as light reflection and spectral absorption (i.e. ...
9
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2answers
302 views

Which of these theories on why light slows in media are true?

This question is similar to previously asked questions, but the responses to them are confusing and I think it may be better covered by listing out all the potential answers for clarity. It's a ...
9
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1answer
1k views

Distribution of star colours in a galaxy

I'm trying to randomly generate a representation of a galaxy. I have some Idea on the spatial distribution of stars within a galaxy, and I can find plenty of material on the colour of stars, but ...
7
votes
6answers
14k views

How many colors exist?

How many "colors" do exist? Our perception: As far as I know, colors are just different frequencies of light. According to wikipedia, we can see wavelengths from about 380 nm und 740 nm. This means ...
6
votes
4answers
5k views

Focusing light into an optical fiber cable

I'm trying to focus light from a flashing light lamp throught two lens into a optical fiber cable which is around 0.8cm in diameter. flashing light: a bulb and then covered by a glass of 7.5cm x 7cm ...
5
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5answers
3k views

What makes Sun's light travel as parallel beams towards earth?

Sun's light appear to travel as parallel beams towards earth $_1$. Sun produces electromagnetic radiations through pp chain and other reactions in Photosphere $_2$. I don't see whether these ...
5
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2answers
1k views

Why is glass much more transparent than water?

There is a related question (Why glass is transparent?) but I am coming at it only from Maxwell's equations. One can determine the skin depth $δ$ for poor conductors like (pure) water and glass using ...
5
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4answers
4k views

What color would a proton be if it were visible to the human eye?

If a photon hits a proton, would it have a color? What color would it be?
4
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0answers
296 views

Possibility of a free-space hologram

Holograms are real. But they are not what sci-fi calls holograms. From a simple geometric optics standpoint we can see that in order to create the illusion of an object there must be some sort of ...
3
votes
1answer
207 views

Refraction: Energy flow, tunneling and Evanescent EM waves

In the full internal reflection case where we have a refracted evanescent wave, If another object is nearby, then we could have wave tunneling phenomenon(frustrated total internal reflection). I am ...
2
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2answers
133 views

What exactly is color? [duplicate]

What is color? “The property possessed by an object of producing different sensations on the eye as a result of the way the object reflects or emits light”…. You might say. So take a white object ...
2
votes
3answers
908 views

What starts the movement of a photon

Although a photon has no (rest) mass, it does have a measurable speed. Its movement can be altered by gravity. A photon "travels". If I turn on a flashlight, seen by someone at a distance, the photons ...
1
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1answer
264 views

What range of light wavelengths can a typical mirror reflect?

A typical mirror is capable of reflecting the full spectrum of visible light. Can it also reflect other wavelengths both longer and shorter? What is the range?
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2answers
133 views

Would passing horizontally polarized light through a varying width vertical slit allow you to measure the positional (x) amplitude of light? [duplicate]

I have found closely related questions on StackExchange, but (surprisingly) not this exact question. Seems some answers say individual photons do not have amplitude, only when traveling with other ...
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vote
1answer
353 views

how many times have the first photons lapped the universe?

I'm not really interested in the actual number of times, but rather an explanation of a closed Universe. How do we still measure the background radiation of the Big Bang? Those electromagnetic waves ...
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3answers
6k views

Why are there no stars visible in this photograph?

Pluto and Charon, photo taken by New Horizons on July 8, 2015 from a distance of 6 gigameters. it's hard for me to believe there were no stars behind the twin dwarf planets in the field of vision. ...
15
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3answers
3k views

Has everything we see happened in the past?

Whatever we see is basically based on the light that hits our eyes, right? When we look at the Moon we are looking at the Moon as it was couple of seconds ago, as the light takes some seconds (~2 ...
11
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4answers
515 views

Does the speed of medium affect the path of light?

Let's say I shine a laser from a stationary medium into a moving medium (suppose the water is moving very quickly) perpendicular to the interface and back to a stationary medium like this: (Note: ...
10
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3answers
764 views

Using a black hole as a mirror?

http://www.youtube.com/watch?v=ENd8Sz0AFOk The YouTube video is a good example how the gravity of this merging binary black holes bend light around themselves.
8
votes
2answers
636 views

Are there “gaps” in light, or will it hit everywhere?

Not sure how to word my question. Picture a light source in vacuum, so nothing disturbs the light (or similar conditions), 2d. If I move very, very far away, will it happen that some of the light ...
8
votes
2answers
737 views

How does infrared light 'erase' phosphorescence on zinc sulfide?

I found some sheets of zinc sulfide in my basement that phosphoresce green for up to 24 hours or so after exposure to bright light in the violet range or shorter. One of the first things I tried was ...
7
votes
1answer
224 views

Is Huygen's Principle Axiomatic?

Is Huygens Principle just a fundamental way to understand light? It always seemed to me that it was somehow "derived" or that it should be-but is it simply a well-founded theory?
7
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4answers
12k views

What invisible flicker do different types of light bulbs have?

What waveform does the light coming off different types of artificial light sources have and (of course) what are the underlying physical reason for them? I was inspired to ask this question ...
6
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5answers
978 views

Can we change a photon's frequency in mid-air?

Can we have a light source emitting photons in the infrared range and after, lets say, 5 meters, these photons become a photon in the x-ray range? The only way I know we can change a photon's ...
6
votes
2answers
591 views

Blue-shifting as opposed to violet-shifting

A recent XKCD comic implies that the sky is blue as opposed to violet due to human physiology, and that animals more sensitive to shorter wavelengths will perceive the Earth's sky as the shortest ...
5
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3answers
3k views

What does the colour of a light bulb depend on?

There are light bulbs of different colors available (red, green, yellow, white, etc). What does the color depend on? Is it on the temperature of the filament?
4
votes
1answer
244 views

What causes these rainbow effects using a polarizing filter on an airplane?

I know that light reflected from a surface at 45° is polarized and that for a similar reason skylight arriving from a direction orthogonal to the sun is polarized too. Photographers make use of this ...
4
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4answers
247 views

Why does it require such little energy to create the fastest thing in the universe?

I have noticed when I turn on the light switch in my house light comes from the bulb. How is this light created?(process occurring in the bulb) and why is this small amount of electricity enough to ...
3
votes
2answers
61 views

Time-coherency of “incoherent” light

Even "incoherent" light as the one of a light bulb has some coherency, and would interfer in the double-slit experiment (even if more blurry because the different wavelengths don't trigger the same ...
3
votes
1answer
109 views

Why are some elemental materials grey?

How does grey occur in elemental materials such as metals? I believe that grey arises from the simultaneous reflection and absorption of all colors of the spectrum (in different atoms of course), as ...
3
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4answers
2k views

What is difference between white objects and transparent objects as far as photons are concerned?

Transparent materials let photons through because the energy gap of electron is so large that the photons cannot be absorbed. If the material absorbs a photon, the photon disappears; does this mean ...
3
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2answers
396 views

Does Light Ever Cease Once Created

I was reading an article on Huffington Post (link to article) about the Multiverse theory. In the article it said this: The big news last week came from the Background Imaging of Cosmic ...
2
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4answers
248 views

What do light wave oscillations look like? [duplicate]

High school physics student here, so please bear with me for a moment. I know that light waves oscillate, but I don't know how. In textbooks and diagrams they're portrayed as wavy lines traveling ...
2
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3answers
139 views

Is sunlight truly white?

I recently purchased a book on nuclear astrophysics, with no goal of mastering the topic but merely to read in between exams and hopefully learn something, it is revealed that the sun is composed ...
2
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2answers
620 views

Can we get the refractive index of a prism by using white light?

Can we get the refractive index of a prism by using white light ? I guess since white light is non chromatic, it is not possible.
2
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2answers
2k views

Calculating the coherence length from a spectrum

I have measured the spectrum of the LED in my interferometry set-up, and now I want to calculate the coherence length from it. A commonly found formula is $l_{coh} = \frac{c}{\Delta f}$, sometimes ...
2
votes
2answers
267 views

Can we have light through out the house with out light being switched on for all the time?

Optical fibres are used to transmit light from one place to the other along curved path in a more effective manner. The optical fibres consist of thousands of strands of a very fine quality glass or ...
2
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2answers
2k views

Do photons actually generate a slight kinetic force?

My question is even though photons have no (rest) mass, do they emit a external force due to EM radiation causing electrons to be excited and jump to higher energy shells which electrons have mass ...