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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How to increase/decrease laser pattern size

I have a laser pointer with a diffraction grating lens that creates a cross-hair, like the one seen below. I'd like to be able to increase or decrease the size of the cross-hair so that it may ...
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0answers
23 views

Curved light cones converge at big bang

Space has expanded manyfold since the big bang, presumably even 1090x since the CMB. Thus our light cones which start out straight must curve inward to theoretically meet at the single point of the ...
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2answers
59 views

Light and mirrors [duplicate]

When I shine a beam of light at a mirror why does the ray go in the exact opposite direction (tested with protractor). Why does it not go back in exactly the same direction? The beam is of an ...
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2answers
74 views

How is light related to photons? [duplicate]

This may seem like a duplicate but I do not understand other explanations. I have read that light is an electromagnetic wave (a fluctuation or disturbance in the electric and magnetic field). How ...
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2answers
70 views

Why is water such a poor electromagnetic conductor? [closed]

1.-Why does salt water not conduct any form of non-visible light? 2.-Why does it conduct red light so much worse than other colours? (Why does it absorb red so much and not blue, for example). It's ...
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5answers
59 views

Dependence of Color of Light on Wavelength?

Recently i saw a question here which asked "what does the color of light depend on as we percieve it?".Now some members answered that if you see an object from any other medium it appears the same ...
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1answer
85 views

How do opaque materials have an index of refraction?

The index of refraction defines how much light is bent as it passes through an object, right? So how can opaque objects, which don't transmit light, have a value for the index of refraction? (e.g., ...
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1answer
102 views

Why don't I see green flames more often?

I was just thinking today that I usually see red flame, and have seen plenty of blue flame, but not green. My naive presumption for coloration of flames would suggest that I would see more green, so ...
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0answers
19 views

Question about Gravitational Deflection of Light

I was wondering if deflecting light around two black holes or more would cause light to come back to the original spot. Such as if light from today traveled near a black hole so it was deflected 50° ...
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1answer
29 views

Will the ray of light follow the laws of reflection at the interface of two media?

Suppose at the boundary of two optical media,of different refractive indices a mirror is kept perpendicular to surface of the boundary.If a ray of light travels through one of the media and then ...
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2answers
58 views

Visible light excitation by heavy particles [closed]

Can I excite visible light from an atom by a proton or muon beam? How would that be possible?
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2answers
48 views

Unusual phenomenon from fluorescent lightbulb

Next to my bed I have a fluorescent desk lamp. One night, after I had turn off all the lights in my room, I grabbed my blanket from the other end of the bed. As I grabbed the blanket, one end of the ...
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2answers
83 views

Is it possible to create an optical medium where sound can travel faster than light?

The speed of light decreases with increase in the density of the optical medium whereas the speed of sound increases with increase in the density of the medium. So is there any possibility to ...
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2answers
37 views

light speed broadcasts [closed]

I’m a writer. I'm working on a story. It’s sold actually, but they want some changes and I’m trying to figure out the science.. IDEA: A distant planet picks up broadcasts from Earth, so the ...
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0answers
30 views

Is it possible to have a 1m2 base at 1m from a source with an angle of 1sr?

Theoretically, a light source with a solid angle and $1\ \mathrm{candela}$ will produce $1\ \mathrm{ lux}$ at a $1\ \mathrm{m^2}$ area $1\ \mathrm{m}$ away. However, when I calculate the base of the ...
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1answer
72 views

What is the physical nature of electromagnetic waves?

I've been trying to work out what the physical nature of electromagnetic waves is, since I reasoned that given electromagnetic waves have wavelengths that are given in distance units, rather than ...
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2answers
61 views

What is the difference between scattering and backscattering?

I sometimes hear people talking about scattering and backscattering, but I really cannot distinguish between the two? Can some one please explain what is meant by these two concepts from a physical ...
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1answer
28 views

how (n) number of eyes can see one dot (for example red dot) from different place at same time?

Today, me and my brother looked at red point of the wall (that was a red sticker for kids), and we saw the red point even we changed our locations in the room, and I can argue that everyone can see it ...
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2answers
62 views

Can a prism have a square cross section? [closed]

Prisms are usually depicted as triangles made from a transparent material such as glass or acrylic. Could a rectangle or a thick sheet of a similar material act as a prism too? I have never seen one ...
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1answer
21 views

Best way for calculating Lux from candela vs from lumen?

Researching this topic, I came across two methods that seem to contradict each other. Need to decide which to use. I am a novice in this field so please be gentle. Also, I would have loved to use ...
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0answers
32 views

How can I change the angle of a laser without mechanical aid

I'm trying to figure out a way I can bend change the angle of the beam coming from a cheap laser diode or laser pointer on the fly. One thought I had was a small prism or mirror that is attached to a ...
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1answer
29 views

The Effect of Camera Lens Extension Rings on Minimum Object Distance [closed]

I found this article on hacking macro lenses. The author used a lens extension tube to increase the magnification of a standard lens into a macro lens. To my surprise the lens's Minimum Object ...
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1answer
43 views

What part of this picture demonstrates the wavelike properties of light and what parts demonstrate the particle-like properties?

Back in march some scientists took the first picture of light as both a wave and particle. I was wondering what parts of the image actually demonstrated these properties. I have some ideas, but the ...
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2answers
94 views

Effect of polarizer on light's intensity

If you take unpolarized light and pass it through a polarizer, it's intensity will be half of what it was (ideally). Following Malus' Law I'd issume that if I pass this now polarized light through ...
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0answers
33 views

Polarization Of Light From A Calculator Display

Okay so I couldn't see anything that matched this, partially because I do not know what aspect of polarization it fits into, but in Physics class we did a practical and as part of an extra bit of it ...
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3answers
69 views

Light interference with light and other EM waves [duplicate]

Lets assume a room with one or two sources of light (normal light bulbs or fluorescent lamps). So if we look at lamp from any direction we see it. We also see different objects in the room because of ...
4
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1answer
176 views

If refraction slows down light, isn't it possible to hold light still?

I have a quick question about the refraction of light, and I'm sorry if it seems a bit simplistic or even stupid, but I'm still learning. We know that when light passes through a denser medium, it ...
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1answer
65 views

Speed of different colours of light [duplicate]

Speed of light is different for different colours. What does the speed of a particular colour of light depend on? Which colour of light has the highest speed?
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1answer
47 views

Why aren't pictures of Pluto darker than those of other planets?

Just as the intensity of the light from a candle decreases with distance, I would expect the light from the sun to illuminate the distant planets less than the closer ones. However, the pictures of ...
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2answers
74 views

How the speed of light is constant in the universe if it decreases in water and glass and some other objects? [duplicate]

My teacher told me that speed of light is constant in the universe. But in optics it is clearly shown that speed of light slows down in some objects. Please help.
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0answers
88 views

How did Maxwell conclude that light is an electromagnetic wave? [closed]

I was looking at the answers for "Why is light called an 'electromagnetic wave' if it's neither electric nor magnetic?", especially the answer by NikolajK that references a Wikipedia article and the ...
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1answer
48 views

Properties of “hard light”

According to this, and this, we now have the ability to make "light molecules", which, from my admittedly layman understanding, have something to do with rubidium atoms, vacuum, and temperatures near ...
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0answers
33 views

Crest in Light Doppler Effect

The way it is explained in wiki Doppler effect in sound happens because waves of particles with biggest density called crest hits our eardrums more often if object is moving towards us (increased ...
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2answers
45 views

Wavelength of light in a gravitational field

I'm having a light source which can emit a particular wavelength of light, on an extremely massive planet. Light will be affected by gravity, So will the wavelength of the light source increase? As ...
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0answers
117 views

Is Wikipedia wrong about Huygens-Fresnel Principle?

Someone posted a question about why backward waves don't exist according to the Huygens-Fresnel principle: Why doesn't a backward wave exist? In following up on this question I read the Wikipedia ...
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2answers
35 views

Can I see the edges of the visible spectrum at home?

So we can modify light outside of the visible spectrum via sophisticated lenses with the result being a new frequency inside the visible spectrum. What I would like to do is different. I would like ...
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1answer
94 views

If photons have mass then how can they travel at speed of light? [closed]

Anything that has mass must be slower than speed of light. If they are travelling at speed of light they must contain infinite energy which should be able to destroy everything, clearly thats not ...
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2answers
77 views

If curved paths imply that the vehicle is accelerated, how come do we assume that light gets curved whilst its speed is constant?

I don't understand how we can accept these two sentences at the same time: Light speed is constant, therefore experiences no acceleration. On the presence of a gravitation field, light path is ...
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2answers
38 views

Space station illuminated by the Earth

Let's say that we have a space station orbiting the Earth around the equator at a speed of 360 degrees per 24 hours, always being roughly on the line between the centers of the Earth and the sun. From ...
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0answers
40 views

Will the flash light accelerate in space? [duplicate]

As we know from school physics course light has pressure. So my question is will flash light accelerate in space in the direction opposite to light emission? If not, then will flash light with ...
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2answers
73 views

At which times does light act as a wave and at which times does it act as a particle? [duplicate]

Is light a "particle", that exists as a photon or as a "wave", the usual electromagnetic wave. If it's both when does it exist as a "particle" or a "wave"????
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4answers
3k views

Why can't I see the blue color scattered by the lower atmosphere of the earth?

I understand that the blue colour of the sky is because of the scattering of blue light by molecules in earth's atmosphere. The scattering appears to be happening from molecules that are far above in ...
2
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0answers
37 views

How does refraction work? [closed]

https://www.youtube.com/watch?v=YW8KuMtVpug&feature=iv&src_vid=CiHN0ZWE5bk&annotation_id=annotation_187211 Start the above video at 8:15. How does the phase velocity affect the apparent ...
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2answers
4k views

Why aren't all objects transparent?

I know that for an object to be transparent, visible light must go through it undisturbed. In other words, if the light energy is sufficiently high to excite one of the electrons in the material, ...
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0answers
29 views

What is the formula for light emission from a point source in scattering media?

I'm trying to model the light output emitting from a point source somewhere in R3, and impinging on a fiber optic at distance r, that may be angled relative to the point source at some angle $\theta$. ...
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0answers
18 views

Modeling total absorption using absorbance of multiple visual layers

I have a question involving light absorbance versus absorption. It applies to a stack of different photoreceptor types. I understand the difference between absorbance, which is basically equal to ...
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0answers
30 views

If we had a radio antenna produce visible light? [duplicate]

If we had a radio antenna produce visible light would it degrade the quality of the antenna due to the light production. How fast would be the degradation?
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0answers
32 views

What is the exact meaning (distribution) of unpolarized light?

Are there statistical properties to unpolarized light? For example, is the polarization of individual particles in an unpolarized beam has a normal distribution or a uniform distribution etc. of ...
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1answer
52 views

Veterans Day Memorial in the U.S

For the ones who know about it: How many more times will the Veterans Day Memorial stones' holes "align" perfectly? Some info from this site: At precisely 11:11 a.m. each Veterans Day (Nov. ...