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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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
88 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 ...
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2answers
532 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 ...
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0answers
31 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 ...
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1answer
29 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?
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1answer
68 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 ...
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1answer
36 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 ...
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2answers
63 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.
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2answers
89 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 ...
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1answer
49 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 ...
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0answers
48 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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1answer
41 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 ...
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2answers
94 views

Gravitational lensing and perspective

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 ...
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3answers
582 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 ...
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0answers
57 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
92 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
77 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 ...
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1answer
40 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
33 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?
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0answers
43 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 ...
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1answer
44 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 ( ...
3
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1answer
219 views

Beyond the gravity of a black hole

http://www.sciencealert.com/the-magnetic-field-just-outside-our-black-hole-has-been-studied-for-the-first-time reported strong magnetic fields escape out of black holes. Does that rule out photons ...
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0answers
90 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 ...
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0answers
68 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 ...
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1answer
112 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, ...
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2answers
302 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 ...
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0answers
36 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 ...
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1answer
32 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 ...
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3answers
103 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 ...
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3answers
42 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 ...
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3answers
596 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.
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1answer
61 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 ...
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1answer
28 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 ...
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0answers
23 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
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3answers
89 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 ...
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4answers
183 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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0answers
66 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 ...
3
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0answers
23 views

Diffraction of rays [duplicate]

To all the physics experts here this might sound like a stupid question, but I give it a try: This is a sketch of how you usually learn about the effect of diffraction in an experiment: Now I was ...
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1answer
26 views

Does the propagation model for a visible light communication system differ based on transmitter?

Would the channel of a visible light communication (VLC) system differ based on the type of the transmitter that is used. in literature I stumble upon reading which explains signal attenuation as a ...
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0answers
32 views

Nature of Particle waves [closed]

My question relates to the properties of a single particle (for example purposes lets use a photon) Forgive me if this subject has already been answered by science, i am not aware that it has been ...
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2answers
27 views

Polarized light in single mode fiber

In single mode fiber the light propagates in two orthogonal planes. Input will be linearly polarized light, which state of polarization will be on output and why? And if there will be some different ...
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1answer
26 views

Correcting Myopia with a Diverging Lens

My textbook says that a diverging lens works by rendering the object a virtual image at the myopic eye’s far point. However, wouldn’t the eye then perceive an object farther than its far point at the ...
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1answer
41 views

Convex mirror cut in half

if I cut the convex mirror in half then how will the image be formed?? suppose I have a convex mirror and I cut it in half then how will the focal length of the mirror change?
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3answers
77 views

Can rotating disk clocked at its center at the speed of light have an outer edge that travels faster than the speed of light? [duplicate]

I have been running this through my head for a few days and I understand I am probably missing something very simple here. If a wheel is spinning the outer edge will travel at a speed that is greater ...
0
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1answer
19 views

If I pass light through a conducting ring will I get an emf induced in the ring? Also if I do get an emf would that not violate energy conservation?

Here is what I think should happen. Light being an electromagnetic wave should have an oscillating magnetic component which should constantly change the flux linked with the conductor. Hence an emf ...
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1answer
48 views

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 ...
3
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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 ...