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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5
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2answers
152 views

Is the color wheel just an optical illusion? [duplicate]

As a kid, I was taught that that blue and yellow make green, yellow and red make orange, and red and blue make purple - forming the subtractive color wheel. As an adolescent I was taught that blue and ...
2
votes
1answer
154 views

Polar ice caps and thermal radiation

I was reading an article on global warming and it said that the polar ice caps, because they are white, reflect a lot of the sun's radiation. The article also has a picture of some houses in England ...
0
votes
1answer
66 views

Some sort of light reflection

One morning I woke up to a text message and picked up my phone but I was not yet fully awake and my eyes had not really gotten its focus. When I stared at the phone I saw two phones. Which is ...
5
votes
3answers
228 views

Why doesn't visible light generate sparks in aluminum foil when microwaves do?

When aluminum foil is placed in a microwave, I see sparks generated by what I assume is dielectric breakdown. However, if I put aluminum foil in visible light (assuming the same intensity), there are ...
1
vote
1answer
128 views

Does gravitational lensing violate Fermat's Principle that light must travel in straight lines?

Does bending of light due to warping of space violate Fermat's Principle or is it that in the principle light goes in a straight line with respect to space (taking space as the reference) and in ...
2
votes
2answers
122 views

Change of hue near shadows

My brother is an artist and he told me his paintings look more natural when he slightly change the hue (color) of the surface near the transition between shadow and light. Here's three examples: (1) ...
1
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4answers
320 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 ...
2
votes
3answers
129 views

How can sunlight be white , but pictures of the sun be orange?

I was thinking about elementary physics today and realised: We learned and proved that sunlight is white. But i don't understand why when you look at a picture of a satellite orbiting the sun , it(the ...
3
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1answer
424 views

Why do most metals appear silver in color with gold being an exception from a scattering and EM viewpoint?

Related: Why are most metals gray/silver? After reading Johannes’ impressive answer to Ali Abbasinasab question of why do most metals appear silver in color with the exception of gold (and copper), ...
6
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1answer
281 views

Huygens wave theory not applicable to lasers or parallel beams of light?

According to Huygens wave theory, every point on a wavefront acts as a secondary source of waves. Using this principle we can never have pretty narrow parallel beams of light right? Like lasers? ...
2
votes
2answers
130 views

How far can you scatter light using a prism?

If I were to scatter light how far do you think it will disperse and what prism is the most effectively scatters light?
2
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1answer
66 views

What is the intensity of this light?

I am struggling with a derivation that calculates the cross sections for Mie scattering and since the incident light is considered to be a x-polarized plane wave I thought that we would have $$I_i = ...
0
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0answers
63 views

How do Newton's particle model and Huygen's wave theory differ in terms of reflection?

I am trying to find a way to argue against either Newton or Huygen through the reflection phenomenon. I know that Newton's particle theory explains quantum electrodynamics but I have no clue how to ...
-1
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1answer
133 views

Can light exist without spacetime?

Since the medium in which light propagates is spacetime, would light be able to exist if spacetime did not exist? Is this like one of those chicken/egg problems, or can light be thought of as a ...
1
vote
3answers
114 views

Why does increasing the flickering speed of a light have a dimming effect?

I'm setting up one of my first circuits. I have a knob to increase the flickering speed of a led. When I increase the flickering speed up to a certain point I am not able anymore to perceive it is ...
2
votes
3answers
179 views

Four questions on color

First, I apologize for being a mathematician and having no scientific background in physics. The following questions on color came up in a discussion at lunch and I would be very happy to get some ...
5
votes
2answers
267 views

Why does light diffract only through slits?

We can see diffraction of light if we allow light to pass through a slit, but why doesn't diffraction occur if we obstruct light using some other object, say a block? Why are shadows formed? Why ...
0
votes
2answers
173 views

What type of electromagnetic radiation strikes the Earth's surface the most?

If you can could you lists the types of light from the greatest amount to the least amount (Ex: Visible, Infrared, Violet).
2
votes
1answer
226 views

Why does a white object lit by a blue light cast an orange shadow?

I was reading this blog post: http://ianstormtaylor.com/design-tip-never-use-black/ Which phenomenon explains this: But I must have been thinking the same thing, because one of those days in art ...
3
votes
2answers
127 views

Colors of light

White light is always said to contain all the different wavelengths of light. Why, then, can we 'make' new colors simply by adding wavelengths? Is it just a matter of our perception, that, when two ...
0
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0answers
47 views

Why stars twinkle but planets don't? [duplicate]

I am not from a physics background. I came to know this while studying probability? Is this because the planets are nearer than the stars so we get average behaviour rather than random. Is law of ...
5
votes
1answer
214 views

Why does the visible light spectrum appear to be circular [duplicate]

I'm not sure if this is an acceptable place to ask this question, as it may have more to do with the biological workings of human eyes than with the physical properties of light, but I'd rather hear a ...
2
votes
1answer
179 views

Could an oscillator at a high enough frequency produce light instead of radio waves?

Considering that light is in the 400-800 THz range, if you had an electrical oscillator that ran at that frequency connected to an aerial of some sort, would the antenna emit visible light, in the ...
11
votes
1answer
316 views

Looking at an iPhone through a Polarizer

Maybe this is more of an Electrical Engineering question, but does anyone know why iPhones looking green/red through a linear polarizer? I find it strange that the light coming out would be ...
12
votes
4answers
473 views

How does interference move energy from destructive to constructive regions?

I recently read (sorry but I don’t have a reference) that interference is not only about destructive and constructive interference but moving energy from destructive to constructive regions according ...
3
votes
2answers
288 views

How can a green laser be reflected as orange?

My friend recently bought a high-powerd pocket laser pen (from China). It is green, and reflects off most surfaces as green. On some orange surfaces, it reflects orange instead. That is to say, we ...
1
vote
0answers
54 views

Is there spatial data loss in light passing through transparent crystal?

There is perfect parallelepipedal bar made of transparent crystal with cubic lattice floating in vacuum. Faces of parallelepiped are parallel to lattice axis. There is image, forming checkerboard ...
7
votes
2answers
291 views

Why is getting a tan in the evening less likely than getting a tan in the morning?

When I was young I read one book in which is written that you get more tan on the morning than on evening even light angle from Sun to Earth is the same. Don't remember exact reason, I think because ...
2
votes
1answer
158 views

Refraction of light in water

Here's a question in a paper based on refraction of light. I can't seem to solve it for some reason. A man looks down at a fish length of 20 cm. His eye is 2m above the surface of the water ...
37
votes
5answers
3k views

Why are most metals gray/silver?

Why do most metals (iron, tin, aluminum, lead, zinc, tungsten, nickel, etc.) appear silver or gray in color? (What atomic characteristics determine the color?) What makes copper and gold have ...
6
votes
3answers
140 views

Can visible light be emitted from a non-thermal source?

I was reading about thermal and non-thermal radiation and I was wondering if visible light can be emitted from a non-thermal source?
6
votes
2answers
606 views

Slowing down light in an opaque crystal for a whole minute

I just read about a team of physicists at the University of Darmstadt, Germany, that managed to completely slow down a beam of light that traveled through an opaque crystal (article here). How is it ...
5
votes
2answers
528 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 ...
2
votes
0answers
55 views

Collimating and homogenizing a divergent tunable-spectrum light source

I have a light source (Xenon lamp) which has the possibility to be tuned over spectral range of 390 - 740 nm with 1 nm spectral accuracy . Bandwidth at each wavelength is about 20 nm . Output ...
-4
votes
1answer
127 views

how can u split the Photon? [closed]

If any equations are there ,for split the light particle, means that i have a 1m length of light just consider that in that who can i split the light particle into 1/2 m length Pls tell
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votes
1answer
121 views

how can u control the speed of light? [closed]

The light traveling a 3 lake km/sec, but Pls tell me how can a control the speed of light, means can limit the speed like 2 lake km/sec are 1 lake km/sec Pls tell me equation
1
vote
2answers
263 views

Diffraction and waves

Sorry about my poorly worded question as i'm not to good at explaining but bare with me so here i go. Does sound come as straight lines like ||||| and become diffracted into curves when it passes ...
1
vote
1answer
1k views

Star visibility in outer space even during the day?

Say I am in a space shuttle and have reached outer space. Is it true that during the day it possible to see stars outside through the window? Do I have to wait until night? Why is this the case?
0
votes
1answer
108 views

The Movement of Light

I've asked several other questions like this, and I know it's a dumb question but I really can't understand. When light is emitted from a moving source, it still moves straight in that source's frame. ...
0
votes
1answer
72 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 ...
0
votes
2answers
123 views

Is it possible for a photon to be at rest? [duplicate]

I know it doesn't really make sense if looking at the photon from the wave point of view, but is there any law of physics which prohibits a photon from stopping completely? Thanks.
1
vote
1answer
131 views

Accelerated Light Sources

When someone accelerates towards a light source, how does the light that's radiating off from it look? I suppose in an inertial frame, all the light should be moving off straight from the source, but ...
-3
votes
1answer
94 views

Describing the path of light from a moving source with waves [closed]

Can anyone explain the path of light to me, using a wave model, that show the angled path in different reference frames?
4
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2answers
2k views

Why does light always travel in a straight line?

No matter the frame light is in, it always moves in a straight line in that frame. Why is that? It doesn't seem like something to me that should necessarily be true. If some one runs forward and sends ...
2
votes
2answers
139 views

Light in Different Reference Frames

I think I'm just confused, but for some reason I thought that light moving straight in one frame would have to move in the same direction in another frame. I know there are photons-but because I have ...
6
votes
1answer
79 views

How far can one look into space while relying on light in the visual spectrum?

Put the other way around. From how far does visible light reach the Earth to be observable by a telescope that operates in this spectrum? Gas clouds for instance absorb light. A star behind such a ...
3
votes
2answers
88 views

Would it be possible to build a Solar Panel Etalon?

Since, on average, 1/3 of all sunlight that hits a solar panel is reflected, wouldn't it be possible to set up some kind of etalon system where the reflected light is then absorbed by another solar ...
-1
votes
0answers
67 views

How to determine spatial color distribution? [closed]

Is there an easy way (i.e. free or open source tool) to determine the spatial color distribution (i.e "intensity") in a picture or in a region of interest of this picture? Let's say I used a laser or ...
25
votes
3answers
3k views

Where does the light go when I turn off the light switch?

As above... Surely it must go somewhere? My child asked me this question and it was a difficult one to answer.