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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2answers
133 views

Convert normal white light to laser-like light?

Is there a probable device that can convert white light to laser-like light without the need of an electrical stage in-between? I'm thinking of something along this level. A very precise filter and ...
3
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1answer
67 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, ...
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0answers
27 views

What does the refractive index depend on? [duplicate]

I've always thought refractive index is dependent on the density of the material. The more denser, the more refraction. But kerosene whose density is higher than water has refractive index less than ...
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2answers
40 views

What is the maximum light difference for one to be able to see into or out of a building and equally discern objects? [closed]

In this question I am referring to the physics behind not being able to discern objects outside when in a lit room, even though you would be able to discern them if you were outside, even though when ...
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1answer
62 views

Why EM waves with long wave length traveles long distance cmpared to EM waves of smaller wave length? [closed]

Most of the times i was told with an example that police uses red light because they travel large distance than compared to blue or green or other wave lengths ? ...
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2answers
123 views

Why do I see things better when they're reflected through my iphone screen?

Sometimes looking at a screen for too long hurts. This happens to me when I use my computer or smartphone for too many hours, and my eyes become tired and weak. Lately I noticed that if, instead of ...
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2answers
435 views

If photons have no (rest) mass, why would black holes attract light? [duplicate]

I was told that photons have no (rest) mass. However I thought that black holes are called "black" because no light can go escape the gravity force in their vicinity. I somehow think that, if light is ...
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2answers
324 views

How we see laser light if it travels in a straight path? [duplicate]

Light travels in straight path, and our eyes detects an object's reflected light then we see the object. So if laser light is going in a straight path, how come we can see laser light?
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1answer
32 views

Duality in Electromagnetic Spectrum

Is visible light the only portion of the electromagnetic spectrum that exhibits particle/wave duality? If so, how/why do other frequencies (i.e. radio) behave as waves?
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1answer
58 views

Light Lab Misunderstanding. Please help

For a Physics lab, this question was asked "As you learned, the wavelength and the separation of the sources affect the number of nodal lines produced. Using your results from steps 2 and 3, determine ...
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2answers
104 views

Why does light from a laser end up in a concentrated spot?

I've heard from several people that photons will always take the past of least action while travelling, so why does laser light projected on a surface appear concentrated to a single spot when ...
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2answers
170 views

What's the intensity of a laser pointer?

The unit of intensity or the irradiance of the light is $\mathrm{W/m^2}$. So what's the intensity of a light pointer? Searching on the web, the laser pointer's power is about $5\mathrm{mW}$, imagine ...
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1answer
194 views

Tunable Optical Band Pass Filter

Is there any cheap method by which to create tune-able optical band pass filter? I am working with a chemical process which will fluoresce when excited by a specific wavelength of light. As shown in ...
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4answers
5k views

How do electromagnetic waves travel in a vacuum?

This is perhaps a total newbie question, and I will try to formulate it the best I can, so here it goes. How does an electromagnetic wave travel through for example, the vacumm of space? I usually ...
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2answers
64 views

When does a monochromatic beam of light on a reflective surface get completely transmitted?

My book says when when a monochromatic beam of light is normally incident on reflective surface it gets completely transmitted. I am bit confused could you explain me?
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1answer
121 views

Detecting a light ray without disturbing it

If I have a light ray trapped between two very reflective surfaces such that the light ray doesn't dissipate, how exactly can I know that there IS a light ray there, without disturbing it? As far as ...
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1answer
44 views

Are there multiple ways to create the same color?

Color is formed by mixing light of different wavelengths, so a color could be represented as a function which gives the amount of light of each wavelength. My question is, if white light is a mix of ...
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2answers
102 views

Capturing a light beam

For a given container made of an extremely reflective surface, is it possible to shine a beam of light in, and with no 'fiddling' (i.e. closing the hole, tilting the object) to contain the beam for an ...
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2answers
346 views

Why do we assume that rays from infinity are parallel?

If light rays are parallel to each other , if they are from infinity, they are not gonna make an image because they won't intersect with each other. So we are not gonna see the image. Does that means ...
3
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2answers
181 views

Which lampshade is brighter?

My room has a single light bulb. It's a bit grim, so I decide to decorate. I have a choice of two lampshades. Both are paper ball designs. One has twice the diameter of the other. The paper is the ...
3
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2answers
156 views

How would a sound mirror work?

Context: We all know that by galvanizing a plate with a silver coating, this plate will have a very high reflection coefficient and act as a mirror for EM radiation (not for all $\lambda$ ranges of ...
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1answer
62 views

Why does yellow line on road seem white at night?

I have observed while driving at night the yellow marks on road seem white. What I understand is the color of an object is the visible light wavelengths it does not absorb. In other words the yellow ...
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1answer
59 views

An accelerated charge produces an electromagnetic wave. Is light an electromagnetic wave despite not having charged particles? [duplicate]

Light is an electromagnetic radiation contrary to the law of electromagnetism that states that: an accelerated charge produce electromagnetic wave. Please explain.
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0answers
45 views

What properties affect the color of item?

I already understand how gap bands work and how atoms can absorb/reflect light. I also already understand that rough objects will reflect light differently in comparison to smooth objects, but I do ...
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1answer
57 views

One color frequency items

I asked a slightly different question before, but how common are one color frequency items? Many things can reflect many colors of light, but predominantly show one under white light. If they are ...
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3answers
2k views

Why is the light reflected at the same angle from mirror?

From the school physics I know that the material objects bounce from the plane surface at the same angle, losing some kinetic energy. In the same school I was taught that the light (and waves in ...
3
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1answer
83 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 ...
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0answers
15 views

Are there any pigments which can be altered via the use of electricty?

I was looking at alternative visual output methods for computer, phone and the like and was wondering, are there pigments, Red, Green and Blue preferably, that can have their intensity/opacity ...
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1answer
183 views

Coherence length requirement for interference

One property of light sources that is usually stated, which is of particular importance when trying to create interference fringes, is the coherence length (or coherence time). The equation for the ...
19
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1answer
3k views

What happens if you remove the polarization filter from a computer monitor?

Have a look at this youtube video (and some extra footage here). Here I will post a gif showing in short what it is about: It shows that if you remove the polarizing filter from a pc's monitor and ...
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2answers
84 views

Why does the ray bend only in one direction?

By snell's law , the refracted ray bend away or towards the normal according to refractive index of the medium. But it can be seen that the refracted ray bends to the right by an angle when a ray of ...
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5answers
882 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 ...
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0answers
38 views

Can we convert light to another spectrum?

Could we convert light from one spectrum to another just like how it does in a radium, using some device? If we could do that to a specific part of the emitted light, probably we could make 3-D ...
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1answer
138 views

Why can't we produce visible light from a radio transmitter? [duplicate]

Producing visible light from a radio wave transmitter: why is it not possible? If it is, what are the limitations?
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3answers
169 views

Relation between wavelength and system size

We always say that when a given light wave interacts with atoms bound in a molecule, only waves with wavelength close to the inter-atomic-spacing are able to probe the system. In other context ...
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2answers
207 views

Light wave crossing media and the relationship between speed, wavelength, and frequency

There are many threads on this topic (like this one) but one aspect about the equation $ v = \lambda\nu $ still confuses me. I have read that frequency does not change when light crosses into ...
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0answers
59 views

Where does light go when you switch it off? [duplicate]

I have a lamp. When I switch it on, it immediately illuminates the surroundings. When I switch it off, the light goes away in an instant. Why is this? Where do the light particles go? Do they quickly ...
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2answers
54 views

Is there a material that could “convert” near infrared frequency to infrared?

I have a laser with a wavelength of 650 nm (visible red light) and was wondering if there is some sort of material that could be used to absorb and disperse a different frequency of light around (900 ...
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3answers
81 views

Does polarization remove any of the fields completely?

A light is made up of electric and magnetic fields oriented perpendicular to each other. Can polarization lead to the removal of any of the fields completely?
3
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1answer
106 views

Light in a box with positron walls instead of electrons

I understand that with a hollow cube with the inner walls covered in mirrors given a light source briefly, the light would eventually be absorbed. This is due to electron excitation I believe. So ...
3
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1answer
177 views

Non-polarised light

We know the beam of light oscillates in electric field and magnetic field, both perpendicular to both the wave of propagation and each other. What does, however, a non-polarised beam of light look ...
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4answers
259 views

How can a 360 Degree Rainbow be formed? [duplicate]

Just a while ago while I was reading news paper, I saw an amazing article. Someone had caught a photo of a 360 Degree Rainbow. But how is it possible. I mean after refraction the only rainbows that ...
2
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2answers
121 views

Is light emitted in zitterbewegung? [duplicate]

Recently I heard of Zitterbewegung, a trembling motion of the electrons in atoms that arises from Dirac's equation. I know that, according to Bohr's model, light is emitted when the electron "jumps" ...
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3answers
274 views

What does amplitude in wavelength of light physically mean?What oscilates with time in photon?

Like amplitude in wavelength of water waves signify the displacement of water particles about their mean position.
26
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3answers
3k views

How does light speed up after coming out of a glass slab?

As I learned today in School, my teacher told me that when light enters a Glass Slab it slows down due to the change in density and it speeds up as it goes out of the Glass Slab. This causes a lateral ...
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1answer
117 views

How do I calculate the apparent brightness of a mirror reflecting the sun at a given distance?

I've stumbled around trying to figure this out, but it just isn't my area and I haven't gotten far. This is for writing about an idea of a field of mirrors on the moon, on the terminator when the moon ...
3
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1answer
122 views

Does irregular reflection form images?

In one of my test papers at school, we had a true-false question which said "Irregular reflection can form an image." I marked it true, however I was not given any marks for the question. I asked my ...
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1answer
50 views

Radiance increase via two sources [closed]

Can two sources of white light shined at the same general location increase the resulting rasiance?
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1answer
24 views

Dynamic equations for propagation of light through dust

For smoothly inhomogeneous media light propagation can be modeled by Maxwell's equations with non-constant $\varepsilon$ and $\mu$. This allows to relatively easily model propagation in the medium ...
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1answer
57 views

Physical effects on light from stars

I was thinking about how we see stars at a distance, the light that travels from them is affected by the Earths atmosphere, gravitational lensing and dust etc., but there doesn't appear any equation ...