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
70 views

Can light be rotated using lenses or prisms?

I was wondering if it was possible, by using only lenses, mirrors, or prisms, to rotate a ray of light coming from a certain direction. For example, if I have two lasers beams side by side, is it ...
1
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0answers
27 views

Can I emit light from an inductor? [duplicate]

As I understand it, inductors create a magnetic field when current flows through them, and light is an electromagnetic radiation. So, is it possible for an inductor to generate magnetic waves of the ...
3
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2answers
63 views

What happens to scattered light when intensity of light increases?

Does increasing the intensity of the incident light increase the proportion of the light that is scattered?
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0answers
42 views

What happens to the group and phase velocity of light as it travels through a medium?

We have all been told that when light travels from, say, a vacuum through water it slows down. What I want to know is what happens to its phase velocity and group velocity. Refractive index is $n = ...
2
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1answer
86 views

Why are red colored object red?

I've read that all electrons want to be in their ground state, so when light from a source is absorbed by the electrons in a red colored object and forced the electrons into higher orbital/energy ...
1
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1answer
47 views

Is it possible to get a lasing from every luminescent media?

Let's assume that there is a cavity with a couple of mirrors and gain media between which possesses luminescence under some external excitation/pumping. Let the absolute quantum yield of the gain ...
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0answers
45 views

How does the sun rise upwards with brightening and set downwards with low fading being stationary on a spinning earth? [closed]

Can someone please apprise me with this phenomena that earth is spinning on it's own axis with 23.5 degrees tilt also rotating around the sun while sun is stationary. when sun is just rising up we can ...
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0answers
25 views

Interpreting LED output distribution specification

I have specifications for an LED which gives the following graph of spacial output distribution. I am not sure how to interpret this. As I see it, it could be one of two ways. To make ...
2
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1answer
92 views

Why do we see just one octave of light? [closed]

When one takes a look at the usual chart of EM spectrum one cannot help but notice that visible spectrum is slightly below one octave of frequencies; that is, the ratio between the highest and least ...
3
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6answers
99 views

visible light spectrum

Why do we see black objects? Colors of objects are formed when the spectrum of that color is reflected. Example Green objects are green because they reflect the green spectrum of light, red objects ...
1
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0answers
19 views

Why is a rainbow in the sky always an arch? [duplicate]

It's been raining a lot lately in the bay area of California (thankfully! keep it coming rain gods!) which puts me and my dad in a contemplative mood. The rain has given us something to contemplate: ...
2
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3answers
871 views

Is white a single color? [duplicate]

We have seen the Newton disc, when it is rotated it produces white color. So I want to know whether white exists as a single color or is that a combination of multiple colors?
1
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2answers
190 views

Red Photon Blue Photon

Why in space red light travels farther and is more observed in dying stars before a star becomes a black hole? while on Earth in water and air the blue light travels the farthest. For example: a ...
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0answers
30 views

What are ways to measure light scattering for a science fair project? And how exactly does scattering work?

How does scattering work? And why? I am still in middle school. I am doing my science fair project on scattering and so far the resources I found have either oversimplified it or made it in a way ...
4
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1answer
101 views

Why are agglomerated gold nanoparticles black?

I put a drop of aqueous red colloidal gold on a glass. After the drop dried I saw that remaining nanoparticles were black instead of red. Why black? Does it mean that plasmon resonance is so strong ...
17
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2answers
606 views

Why does William Herschel's experiment show red light as warmer than blue?

Why does William Herschel's experiment show red light as warmer than blue if blue light is higher energy? Here is an explanation of Herschel's experiment ...
1
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0answers
32 views

Can you grow more Biomass in a brickhouse only powered by solar cells than in a greenhouse? Will we ever be able to? [closed]

Right now I read that 1m² of solar cells generates roughly 100Watts of energy. There are really efficient Grow LEDs that use only two spikes in the lightspectrum to make plants grow. I have seen some ...
-2
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1answer
34 views

White and reflections can it absorb and give off heat [duplicate]

Does white give off heat when It reflects light? Can white absorb heat at all or just reflect all wavelengths?overall does white just reflect or can it absorb too?
3
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1answer
83 views

White LEDs and colour perception

I’m very interested in LED lighting and the different spread of wavelengths that are produced compared to other types (like tungsten). Given that a White LED bulb actually produces 3 different peaks ...
0
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1answer
48 views

Kerr Effect; Electro-refraction

First post here. is is possible to observe the Kerr effect in transparent materials, at low voltages (such as 3.8V)? If so, can you refract light enough to distort an image, in a way similar to that ...
1
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2answers
99 views

Why doesn't silicon emit light? [closed]

Why doesn't silicon re-emit light when light falls on it? Or if it emits light then why we can't see it?Hence it has valence electrons.
1
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2answers
117 views

Why does a light wave fade as it travels through space?

It stands to reason: if it didn't, the entire sky would be covered with stars shining blindingly day and night. But what causes a light wave (or an electromagnetic wave) to fade if there are no ...
-2
votes
1answer
59 views

Effects of gravity on light on the surface of the Earth [closed]

I read over the question and answers on the effects of gravity on light. I would like to ask a more specific question about gravity and light. What is the effect of gravity on light on the surface ...
0
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0answers
53 views

Could we have blue/violet shifting?

As the universe expands, it stretches light into longer wavelengths, resulting in what we know as red shifting. But some say that there is a chance in which the universe will stop expanding and then ...
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0answers
15 views

Angular Optical Resolution [duplicate]

Can a series of optical telescopes from orbit (like the radio Event Horizon Telescope) see an object with higher resolution not possible with one telescope?
1
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1answer
58 views

How to explain Doppler redshift of light?

For other waves like water or sound, it is easy to understand Doppler effect, because for those waves, the speed of wave in different inertia reference frames changes. But for light wave, the speed ...
2
votes
2answers
120 views

With gravitational lensing could we see our selves from a right angle?

When looking at a black hole the ability to see ourselves is compromised by the small window for the light trajectory to come back to us. The light from the Earth that is bent by (almost) 180° and ...
6
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3answers
592 views

How can light emit three kinds of spectra?

In case of black-body radiation, radiation gives continuous spectra. Molecular spectra is an example of band spectra. Similarly, there's also the atomic spectra. Why are the spectra of light not same ...
2
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0answers
60 views

Stupid physics in cartoons [closed]

I have never really thought about some of the horrible thought (or was it intentional?)physics in old cartoons (for me, I'm 14). The main show im talking about is this stupid one called something like ...
3
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1answer
106 views

How do hotel peepholes only work in one direction?

Basically the title. Light can go into my room through some lenses so that I can see it, but light can't escape my room so that people outside? The article about peepholes on Wikipedia doesn't ...
4
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0answers
93 views

Energy absorbed in Polarization of light

A polarizer absorbs all light that vibrates in a particular direction. Where does the energy absorbed by the "chain molecules" of the polarizer go? Does it change the structure of the molecules? Is ...
0
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1answer
41 views

Can we consider light from the Sun during sunrise and nightfall as polarised?

On sunrise and nightfall light looks different, more orange or more dark. Some frequencies are filtered or light travels longer. The energy corresponding to this light is obviously lower than light ...
3
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1answer
34 views

Recognizing linear or polarized light and seeing its direction

I was watching Walter Lewin's course, and he said he learned a way to see and recognize polarized or linear light. And i wonder what it might be? What is the tricks?
0
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0answers
44 views

Two-slit experiment, why $\exp(ix)$ and $\exp(-ix)$?

I am looking at an example problem from optics with two narrow slits with light shining through both. The light through one slit is 5 times the amplitude of the light through the other. I know from ...
1
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1answer
48 views

The property of transparent lens [closed]

My question is this : what is the property of transparent material that is used for lens?. I think that it allows the light to pass through ( absorption property) and does not bend the light ( ...
1
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0answers
97 views

Can photons be seen with naked eye? [closed]

Whenever I observe the light very carefully I observe many tiny circles of light . I guess these're photons .I'm I right ? If these were photons then it means that they are relatively larger then ...
1
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0answers
92 views

Why do our eyes only pick up electromagnetic radiation which has been classified as visible light?

My understanding: Electromagnetic radiation is carried via photons - which enter our eyes and activate receptors depending on the amount of energy the photons have when hitting them. At what point do ...
-1
votes
1answer
157 views

What is the underlying physics that makes Li-Fi “100 times faster” than Wi-Fi? [closed]

Consider this webpage, which compares how the two work. Particularly it says (and I'm paraphrasing) that Lifi transmits using light from LED bulbs and WiFi uses radio waves. Well, both are EMF waves, ...
7
votes
3answers
543 views

What determines the sharpness of a shadow?

What are the factors that affect the sharpness of a shadow? I would think that the distance between the light source and the object, the distance between the object and the shadow, and the size of ...
0
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0answers
40 views

Is a Battery to store photons possible?

@MISC {55768, TITLE = {Why can't we store light in the form of light?}, AUTHOR = {AldCer (http://physics.stackexchange.com/users/20409/aldcer)}, HOWPUBLISHED = {Physics Stack ...
0
votes
1answer
63 views

Light's wavelength and pathlength

I see this 2 words (wavelength and path length) used interchangeably. As interpreted here: 'The total power density arriving at the surface depends on the absorption path length of the light ...
4
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3answers
129 views

Why is visible light easily blocked by pretty much anything but radio waves are not?

Light (visible part of electromagnetic spectrum) is easily blocked by most materials. Radio waves are not but also X-rays are not. What is so special about this small part of the spectrum since both ...
0
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3answers
48 views

Can light from the same source interfere with itself without utilizing n-slit screens?

I was wondering - can a source produce light which travels in such a configuration that part of it travels a longer distance (i.e., is out of phase with its other part) thus exhibiting an interference ...
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.
0
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1answer
79 views

What is the trajectory of a photon moving through a vacuum?

Since electromagnetic energy is carried by photons and moves in forms of waves, does it mean that a single photon when propagating through space doesn't follow the straight path but instead always ...
0
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1answer
31 views

Does scanning a lightsource affect the scan result?

I'm very much a layman on this kind of topic, so my logic may be wrong, but here goes: Sample situation A 'pass app' on your smartphone, allowing someone to scan your ticket on your device. My ...
1
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0answers
41 views

What is the difference between the angle of incidence, refraction and deflection? [closed]

If a ray of light is passed through a piece of rectangular acrylic as shown in image below, how can i predict the deflection of the ray? Should i look at the angles angle of incidence, refraction or ...
2
votes
3answers
97 views

Energy in one wavelength

I know that the energy of one photon equals $E=hf$ and that concept of photons came from the photoelectric effect. My question here can we assume that a photon equals one wavelength for example if we ...
0
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4answers
312 views

Why doesn't a lighter flame cast a shadow?

Light has always been a mystery for me. When we do a simple experiment of holding a lighter in one hand and a light source behind it, it shows no shadow on the wall at all. Why is this happening? Is ...
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votes
0answers
93 views

Which light bulb will burn out? [closed]

We have 5 light bulbs connected in series assuming all bulbs have identical characteristics. The environment is identical for all bulbs. Wire is superconductor (0 Ohm) and is thick enough to deliver ...