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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4answers
113 views

What makes Sun's rays travel parallel towards earth?

Sun's rays appear to travel parallel towards earth $_1$. Sun produces electromagnetic radiations through pp chain and other reactions in Photosphere $_2$. I don't see whether these reactions ...
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3answers
244 views

Question on Radiance equation

The radiance equation is $$ L = \frac{d}{dA} \frac{2(\phi)}{dW cos(\theta)} (watt/srm^2) $$ where $\phi$ is the flux. I am thinking, should not be the cosine term on the numerator instead of the ...
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1answer
48 views

Information in twisted light

New Scientist has a story on the use of twisted light to store multiple bits of information per photon. What is this technology, and what are the information density limits per photon? "MOZART and ...
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5answers
708 views

Radio antenna producing waves in the visible spectrum

If a radio could produce waves in the visible light spectrum, what would the result be? This is a thought experiment that I've pondered for a few years now. I realize there are a few/many real-world ...
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3answers
2k 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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0answers
34 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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3answers
81 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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1answer
54 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
49 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?
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2answers
36 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
34 views

The ratings for light bulbs [on hold]

I have been asked at my job what the ratings are for a light bulb (car beams) 3000-14000k? Can someone find out more about this as the packages don't have any source of info about these ratings. ...
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0answers
34 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
42 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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1answer
174 views

photon polarization, uncertainty in Energy

A beam of red light is sent along the $z$ axis through a polaroid filter that passes only $x$ polarized light. The beam is initially polarized at $30$°, and the total energy is $10$ Joules. Estimate ...
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0answers
15 views

Filtering UV Light to Visible Light [closed]

I'm wondering if it is physically possible to filter UV light from 400nm to 100nm so that UV light is in the visible range. If we had a UV screen over a visible range screen, could there be two ...
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6answers
4k views

Is it possible to witness a circular rainbow?

What conditions would make it possible to see a naturally occurring fully 360° circular rainbow? Would it even be possible?
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2answers
109 views

Light-Matter Interaction and Object's Appearance

I am taking a course in Computer Graphics, and the teacher said we could put materials in there main categories: mirror like glossy or specular diffuse He suggested that the law of reflection is ...
3
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1answer
98 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 ...
2
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1answer
49 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
45 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 ...
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2answers
67 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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2answers
75 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.
36
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9answers
4k views

How would night sky look like if the speed of light was infinite?

Would it be brighter? Different color? Gravitational lensing? Would black holes exist?
2
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1answer
51 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
78 views

Why seeing further in “timespace” does not add up?

I've read that astronomers have received a light (a photon) 13 billion years old. Here's my question: If we start to turn the clock backwards all matter, energy, etc should start heading to the ...
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1answer
31 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 ...
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10answers
412 views

How far can light go?

When a ray of light is projected, (say) from the surface of Earth to outside in space. The condition is that, there is no obstruction to it till infinity (it travels only in vaccum). My question is ...
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1answer
39 views

Radiance increase via two sources [closed]

Can two sources of white light shined at the same general location increase the resulting rasiance?
4
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1answer
3k views

Purple doesn't occur in rainbow - or does it?

Usually, when asked whether the purple color exists rainbows, an answer similar to this is given: The purple color is perceived by human eyes via the activation of both red-sensitive and ...
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1answer
16 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
41 views

Can we get a true negative of an image reversing the spectrum?

In photography the negative means the lightest areas of the photographed subject appear darkest and the darkest areas appear lightest. But I was wondering: is this the way how negative should ...
0
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1answer
44 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 ...
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4answers
9k views

What is the color of a mirror?

A mirror couldn't be white, as then you wouldn't be able to see your reflection so clearly. It wouldn't be transparent, as that then won't reflect. So what color is it?
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2answers
453 views

Are shadows underwater “wet”? [closed]

Sorry if this is the wrong place to post this but it seemed the most appropriate. I read a riddle earlier today that mentioned something about shadows underwater and it got me thinking.. Would a ...
-7
votes
5answers
451 views

Is velocity of light constant? [duplicate]

There is a difference between the concept of the speed of light and the velocity of light. are both of them constant ($dc=0$ and $dv_c=0$)? if yes, why?.
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3answers
10k views

3d holograms - How are they created?

How do 3d holograms work exactly? I read that there is a laser in use, but how are the multiple perspectives generated and how is the light trapped? in a certain area to create the effect? ...
3
votes
3answers
67 views

Negative frequency contributions for very short pulses?

I am wondering if very short optical light pulses can have a Gaussian envelope? When I describe the pulse shape with a Gaussian than the frequency distribution has also a Gaussian shape. But if the ...
3
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1answer
53 views

Bending light (photons) into an orbit

I was wondering and researching about light bending and reflection - I'm wondering if its possible to bend a light beam into a loop (orbit)? I know that light can be bent and reflected (even 100% ...
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1answer
140 views

Scanning electron microscope imaging

In a scanning electron microscopy, secondary electrons are defined as the electrons which obey inelastic scattering whereas backscattering electron follow elastic scattering. Now my question ...
3
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2answers
135 views

A mirror in the sky to look at past Earth

Earth reflects light from Sun into Space; are there any "mirror like" objects which reflect back to Earth this light? Has anyone been able to use this method to recover some information on how was the ...
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4answers
151 views

Why Light isn't like an Acoustic wave?

I just wanted to know why light isn't an Acoustic wave.Is it because light wave doesn't obey acoustic properties?
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1answer
58 views

Path Difference Due to Angled Incident Light

If light incident on a diffraction grating makes an angle $\alpha$ with respect to the normal to the grating, show how $$m \lambda = d\sin\theta$$ becomes $$m\lambda = d[\sin(\theta - \alpha) + ...
2
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4answers
109 views

Space orientation of light waves

Recently I've started to be really intrigued with the electromagnetic spectrum and bumped into this problem: According to the wave theory of light (or any electromagnetic wave, really), the magnetic ...
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2answers
3k views

Is turquoise closer to blue or green?

I am having a discussion with my coworkers. Does anyone know what is the wavelength of turquoise color and whether it is closer to green or blue when comparing their wavelengths ?
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2answers
52 views

Attributes of a polarized light

Which of the following is true for a polarized light? The electric vector is constant in its module and direction The electric vector oscillates in every plane that passes through the ...
2
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2answers
324 views

Finding the illuminance from a triangular light source

Since most light sources in games are point-like, it's pretty difficult to approximate area light sources with point sources. As triangles are a universal form to represent 3D models (thus area light ...
0
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5answers
326 views

Can we create invisible things?

We are able to see this beautiful world because of light. When light gets reflected from the object, the reflected light enters our eye retina and thus we are able see that particular object from ...
0
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0answers
40 views

Why can't we see Rainbows from its end points? [duplicate]

We see Rainbows many times, but we always see them Horizontally or from Sideways. Why can't we see it from under it?/From the point where it starts or ends(end points)? I also want to stress on that, ...
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1answer
52 views

How does Huygens Principle explain interference?

How exactly does Huygens theory about the propagation of wavefronts account for interference?
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2answers
1k views

Squinting at street lights

Simple question, I've always wanted to know the answer to this. Why do you see a pair of lines radiating out from street lights when your squint at them? I can't think of a better way of describing ...