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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7
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2answers
447 views

Why do electric sparks appear blue/purple?

Electric sparks tend to appear blue or purple or white in color. Why?
0
votes
2answers
41 views

How to use a magnifying glas or any lens to enhance small light power?

I am currently trying to amplify a tiny amount of light so that a photodiode will recognize it. In order to amplify the light I thought about using a magnifying glass since I got to know that such ...
0
votes
1answer
21 views

How bright would the Earth be at night without the moon?

How bright would the Earth be at night without the moon? Specifically, how much light would reach the surface of the Earth at sea level?
3
votes
1answer
96 views

Is it possible to apply force to a light particle?

I know, the universal speed limit is the speed of light $c$. So, is it possible to apply more force to a light particle? What would happen to it if we could?
0
votes
0answers
17 views

Visible Color of the sun as a function of time since sun rise

I need functions of Red, Blue and Green colors wrt Time since sun rise. that is sunrise at t=0 as t increases the values of Read, Blue Green will change as a function. We know at beginning of ...
2
votes
1answer
90 views

If the effects of gravity cannot travel faster than the “c”, does this mean we are only gravitationally bound by masses in our observable universe?

I'm 17 and fascinated by the differences and omissions Newton made in his equations of motion. However it makes sense that gravity can't travel faster than light because of the force-carrying ...
0
votes
1answer
15 views

What is the fraction of the incident intensity passing through polarized sheets?

Unpolarized light is incident on a set of three polarizing sheets as shown in the figure at right. The polarizing directions of the sheets make angles 10°, 55° and 85° to the vertical. What fraction ...
5
votes
1answer
842 views

Why is the shadow of a wind turbine a bit slow at first then very quickly, etc. and not equivalent to the wings?

When I stand at a wind turbine and look at the shadow on the ground, the shadow is a bit slow at first then very quickly, etc. Very strange.
0
votes
0answers
5 views

Velocity Selective Coherent Population Trapping and recoil limit on temperature

I have read that it is possible to go under recoil temperature limit using VSCPT (Velocity Selective Coherent Population Trapping) and that this method is based on atoms trapping in quantum state in ...
0
votes
1answer
17 views

What happens to the skin when UV light burn you at the beach? [on hold]

I mean, I'm at 8th grade and I'm studying Physics, actually I'm loving them and I love to know how world works, I read about the Photo-Electric effect, light as a particle can quit electrons to a ...
1
vote
1answer
23 views

photon absorption by atoms causes heat?

I have came up with a weird doubt: photon absorption by atoms causes heat? I mean, I was always told that if the photon's frequency is the magic one, the atoms absorbs the photon and goes to an ...
0
votes
0answers
48 views

Speed of light, comparison of two light waves travelling side by side

okay so.here is setup of my question...say we have two observers A and A'..A is fixed to origin of coordinate axis x,y while A' is inside a hollow box (shown as rectangle MNRP) whose one side MN has ...
0
votes
1answer
22 views

Semiconductors light emission

Suppose a pure semiconductor, with a direct gap. If I apply a constant voltage to it the electrons will jump to the conduction band. So when I turn it off will it emite light?, because the electrons ...
34
votes
4answers
4k views

Do rainbows have ultraviolet bands and infrared bands?

We have seen that rainbows looks so colorful as we are only able to see the visible light only. Do they also have ultraviolet bands and infra-red bands, that we are unable to see? I know someone has ...
-1
votes
0answers
22 views

Origin of inflation [closed]

I have a theory as to the understanding of how inflation occurred and what stopped it! Could someone on staff comment on it please? It goes like this, At the moment of the big bang all of the matter ...
0
votes
0answers
17 views

Why does a circle of light form around a wire when a laser is pointed at it? [duplicate]

Referencing this video: https://www.youtube.com/watch?v=9Q_4SNbpBfo Why does a circle of light form? I've seen previous Phys.SE posts on this topic relating the answer to reflection, but I have ...
3
votes
2answers
46 views

Decoherence of a Coherent Beam

If retarding films (i.e. wave plates) can retard the electric components of light (based on the films thickness) without affecting it's direction, couldn't I use a retarding film of randomly varying ...
0
votes
2answers
58 views

Why do two beams of light pass through one another without interacting?

Why is it that if I have two torches, each shining rays in perpendicular directions at perpendicular screens, such that the beams cross, then the images on the respective screens are independent of ...
2
votes
0answers
17 views

Odd order of colour fringes around cloud

The other day I took this photograph of a thundercloud that moved between myself and the sun. Around the edge of the cloud there were some coloured fringes that I first took to be a variant on a ...
2
votes
2answers
32 views

How is the backlight in a LCD monitor dispersed equally?

How is the backlight in a LCD monitor dispersed equally? I mean are there any layers that disperse the light?
1
vote
2answers
49 views

Would passing horizontally polarized light through a varying width vertical slit allow you to measure the amplitude of light? [duplicate]

I have found closely related questions on StackExchange, but (surprisingly) not this exact question. Seems some answers say individual photons do not have amplitude, only when traveling with other ...
-1
votes
0answers
15 views

Why don't we see a totally circular rainbow in the sky [duplicate]

We know that the rainbow is formed due to the scattering of light. We always see the rainbow in a semicircular style. Does it is possible that we can ever see a totally circular Rainbow.
0
votes
0answers
22 views

Why the underside of an object isn't a different colour after light reflects off a different coloured surface

If you were to place a blue plate in front of a green background and shine a light at the blue plate. The light that hits the blue plate would reflect the blue wavelength and when the reflected ...
1
vote
0answers
11 views

Polarization in LCDs why the light need to be polorized twice? [closed]

In Lcd Screens there is a prcess called polarization. Two question about it: 1. Why is it needed to pass the light through two polarizers ? 2. How des a pixel devide the light to three sub pixel and ...
0
votes
1answer
57 views

Is Lorentz transformation applicable of light itself?

I've just studied Einstein's Special Theory of Relativity and have followed most part of it. I was just wondering that whether the equations of Lorentz transformation are applicable on light? i.e. can ...
0
votes
1answer
68 views

Is it possible to produce coherent light with a thermal source? [closed]

Coherent light means monochromatic light and alle waves have the same phase difference. This is given for laser, where the resonator is a potential box and the outgoing waves have the same phase ...
0
votes
2answers
50 views

Frames of reference and why are they different

Here is a quote from "The Elegant Universe" by Brian Greene. Imagine two countries that have been at war are sitting down to sign a treaty ending hostilities while traveling aboard a train that is ...
2
votes
1answer
32 views

Filming light in slo mo

So I was thinking of a cool video I could make when I thought of filming a video of me turning on a light. I thought that if you film yourself turning on a light and slo mo that video enough times ...
1
vote
1answer
18 views

Relation between temperature and black body radiation

How can one derive the amount of light as well as the shortest wavelength of the emitted light from the temperature of an object due to black body radiation? Shouldn't the amount of light emitted ...
2
votes
1answer
73 views

If atoms are mostly empty space, why doesn't light pass through everything?

Atoms are mostly empty space, and although I now understand why matter doesn't pass through other matter, why don't photons pass through the empty space of the atoms? Is it the same sort of idea as ...
1
vote
1answer
23 views

Do the mediums decrease or increase the speed of light? (source to target) [duplicate]

If sun is the source of light then is it possible that the speed of light might increase depending on the mediums its going through or its not possible.
3
votes
0answers
52 views

Fastest path of light [duplicate]

Fermat's principle of least time says that light always takes the fastest path to any point. So how can light know which is the fastest path without taking all the paths first?
-2
votes
1answer
75 views

Are we working in the double slit argumentation with destructive interference arguments?

Stimulating water with two long straight bars one could produce linear waves. Having the right distance between the bars and the correct frequency of the steady system we get in the middle between the ...
21
votes
3answers
3k views

Why isn't the color of a molecule a combination of the colors of its component atoms?

I was watching a documentary on youtube regarding Quantum Physics when it introduced the wavelengths of light emitted. Did a bit more research over the internet and I believe I understand the gist of ...
1
vote
1answer
61 views

How do I convert lux to lumens

Overview... I'm a novice in the very basics of light physics and calculation between various units. I'm sure this is a very simple problem to those who know the process. And, before we continue, this ...
12
votes
2answers
3k views

Is true black possible?

Black is the absence of light because it absorbs light, but when we create black paint or black objects, light is always reflected, either in all directions in matte or smoothly in shiny black ...
5
votes
0answers
79 views

Why can I turn light red or blue by holding my finger up to it?

This is a difficult phenomenon to explain. Imagine you have an opaque object partially covering a very bright light source, for example, an object held up against the sky. The left hand diagram is ...
2
votes
1answer
30 views

A half covered lens

Let's say there's an object in front of a convex lens. I have a piece of paper behind the lens at the right location such that it will the lens will form an image on the paper. The object is ...
0
votes
0answers
38 views

Relativity - Diffraction Of Light

Following thought experiment. Inside a rocket, right in the middle, we place two lasers pointing in opposite directions. Both emitting the same wavelength. The Left wall of the rocket is L1 while ...
1
vote
1answer
38 views

Is redshift possible if relative speed is 0?

Since we are in a galaxy that is moving 1M mph, and the speed of light is constant, is redshift affected by whether you are facing toward or away from the direction the galaxy is moving? Suppose you ...
0
votes
2answers
96 views

Could time dilation bend the path of a photon? Does time dilation have a refractive index?

The main question I am getting at is, does time dilation have a refractive index? What I mean is, if I were to shoot a laser past a black hole, would the laser's path "bend" strictly from time ...
2
votes
1answer
40 views

My glasses seem to be polarizing the light when they want. What is happening?

When I put the glasses on and I look at my computer monitor and I turn in a certain angle everything becomes black. When I do it on my laptop screen though I need a different angle. Finally when I ...
1
vote
2answers
57 views

Do rainbow shows spectral lines?

A spectral line is the electromagnetic radiation emitted when the electron jumps from higher orbital to a lower orbital of an atom. Water mainly consists of two elements namely hydrogen and oxygen, ...
0
votes
1answer
43 views

Converging light

Imagine that we emit a light pulse. As is the nature of light, it will expand. However, light is affected by gravitational fields and light has its own. Therefore, will the light converge given ...
1
vote
0answers
17 views

About atomic transitions

I accomplished my homework but it opened a whole pandora's box of things I do not quite understand, so I would appreciate help. In x direction linearly polarized light excites atom transition from ...
3
votes
3answers
58 views

Principle of Sufficient Reason on light travelling in straight line

I was reading a book Laws and Symmetry by Bas C. Van Fraassen I found that there is an argument for arguing that light travel in straight line: Leibniz's reconstruction of these arguments goes ...
1
vote
2answers
89 views

Speed of light and perception

So I'm reading a book called "The Elegant Universe" and here is a part of it Imagine two countries that have been at war are sitting down to sign a treaty ending hostilities while traveling aboard a ...
0
votes
1answer
36 views

Can high-power LEDs remotely control a whole room? [closed]

Let's say I have 4 appliances in rectangular based room of about 60 square meters with white walls. The appliances are using infrared receivers with a filter of 38 kHz. Would it be possible to apply ...
2
votes
2answers
74 views

Is light a particle with EMF or does it travel in wave? [duplicate]

Is light a particle which has a electromagnetic field around it OR does the particle itself travels in a wave like motion? IS it just the EM field which moves in a wavy motion like ripples? (Please ...
1
vote
1answer
13 views

Do electric sinusidal waves rotate 45 degrees too when light pass through a hollow cylindrical magnet or just the sinusoidal magnetic waves do that?

Do electric sinusoidal waves rotate 45 degrees too when light pass through a hollow cylindrical magnet or just the sinusoidal magnetic waves do that?