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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Are there datasets with light spectrum samples and their respective 1931 CIE XYZ values?

I'm developing a software (.NET/Mono) library to work with color spaces and light spectrums, and I want to add many test cases in order to ensure software quality. I've programmed code to convert ...
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0answers
17 views

What's so special about the invention of Blue LED that a Nobel was awarded to its invention? [duplicate]

Why was this years Nobel Prize for Physics awarded to Isamu Akasaki, Hiroshi Amano, Shuji Nakamura for inventing the Blue LED? I know that if a Nobel Prize is awarded for an invention, it must be ...
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0answers
29 views

What makes fluorescent lamps lower in heat than high pressure lamps coated with phosphorus?

Why does a fluorescent lamp give off more pure visible light (without heat) than a high-pressure lamp? Is the heat given off by high-pressure lamps caused by the intensity of light being emitted from ...
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0answers
66 views

Use mirror to see every angle around me

An applied physics question: How can I setup a mirror all around an arm wrestling table so I can see all angles of what I'm doing? The arm wresting table looks like this With the wrestlers on ...
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0answers
38 views

Analogy for Rayleigh scattering

This morning's eclipse has me looking into Rayleigh scattering. I'm trying to think of a good analogy to explain it to somebody without getting too in-depth into electromagnetism and other subjects... ...
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0answers
176 views

Nobel prize for (dangerous) LED lamps? [closed]

There are many scientific articles about the danger of LED lamps (see below from the LED magazine, from scientific american, from a governmental journal and from Harvard health newsletter): Light ...
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0answers
67 views

What is this light pattern caused by LED matrix street light?

At our office, they have installed new downlights in the parking lot (street lights) based on a rectangular matrix of very bright LEDs, which are not diffused. They look something like this one: ...
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3answers
98 views

Why is the Moon not redder at moonrise/moonset?

Okay we all know about Raleigh Scattering, which makes the sky blue. And by the same token, sunsets appear red because sunlight traveling through more atmosphere will "lose more blueness" as it's ...
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1answer
83 views

How do mirrors look & behave atomically?

I was observing mirrors recently and I was thinking about how an mirror would look atomically. I was always used to looking at atoms as being colored that said, I was always concerned at how they ...
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2answers
48 views

constant speed elevator light beam paradox

I can't get my head around this problem. Suppose there is an elevator moving up at a constant speed relative to an observer outside of the elevator, far away from any gravitational effects. Suppose a ...
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1answer
56 views

How can monitors display a sharp image, if light travels in all direction?

The question title might be a misnomer, help me improve it. My question is, from my understanding, a light travels in all direction from it's origin point. Also I assume that in the example of a ...
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2answers
548 views

Homemade Spectrometer

Recently I have had ideas of how to build a spectroscope, but I'm not sure if it will work. As can be seen in the diagram, the experiment is simple: it consists of a laser that generates the light ...
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2answers
100 views

How does the human eye knows how far the object from which the photon was reflected?

A photon is emitted from a source and reflected off an object (or objects) until it hits the human eye. The color of the object we see depends on the photon wavelength. If photon travels with constant ...
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2answers
4k views

Why does my wooden door disperse light into a rainbow color spectrum?

On a clear morning, light comes through this window (viewed from the inside) It then hits the door on the opposite side (so viewing from the outside the door straight on the other side) There is ...
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0answers
62 views

Intensity of Brightest Fringe of a multi-slit Diffraction

Let's say we have a multi-slit experiment with N slits.Since the central fringe has the most intensity, is there an equation to calculate the intensity of central fringe in terms of the intensity of ...
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1answer
42 views

How to get the direction of bending light?

When light passes from a more dense to a less dense substance, (for example passing from water into air), the light is refracted (or bent) away from the normal. My question, is there any ...
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3answers
204 views

What “exactly” happens when a ray is incident at the critical angle?

The question arose when my physics teacher taught me geometrical optics and told that the phenomenon of both refraction and $reflection$ occur by change in medium. First of all, I'm not sure about the ...
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3answers
477 views

What happens to photons after they hit objects?

If I am not wrong when light hits for example white wall most of the photons are absorbed and transformed into heat and few of the photons at certain wavelength are reflected from the object. So white ...
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3answers
949 views

Why is the sky dark at night? [duplicate]

The question is the well-known Olbers' paradox: If there are so many/infinite stars, in every direction, why is it dark at night? Where goes all the light we don't see? Discussing with a friend ...
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4answers
7k views

Why is the sky never green? It can be blue or orange, and green is in between!

I, like everybody I suppose, have read the explanations why the colour of the sky is blue: ... the two most common types of matter present in the atmosphere are gaseous nitrogen and oxygen. ...
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0answers
35 views

Rotating sheet of light

I am looking for references on "rotating sheets of light" generated from a point source. Mainly I am looking for applications. (I saw a use related to climate studies or weather forecasting, where a ...
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1answer
63 views

Is the glass made up of holes that let the light to go through it?

The following passage has been extracted from the book "The Magic of Science-A.Frederick Collins" (1917): Substances of all kinds have pores or holes in them. A sponge has pores that can be ...
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0answers
14 views

What are the factors affecting transparency and color of a substance [duplicate]

What is the reason behind visual properties like color and transparency of different substances? I have always heard that the structure of the substance is responsible for these properties. I always ...
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0answers
23 views

Appearance of the recomposition of a given spectrum? [duplicate]

Given a visible spectrum, i.e. a function from the set of visible wavelengths into the set of intensities, I would like to see the color having this spectrum decomposition. Question: How can I do ...
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1answer
43 views

What is the best angle to see water

Sometimes when I clean my house, I miss some of the water since it seems invisible, but when I stand in different angle from the water I can see it clearly, whereas some angles offer partial ...
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1answer
41 views

Why do roads appear wet on hot days? I do not understand [duplicate]

Why do roads appear wet on hot days? I don't understand the bending of light rays in relation to the density fluctuations. How are they related? Why do we see mirror images of cars on road in hot ...
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2answers
90 views

Did Newton argue that particles speed up when entering a more dense medium?

Statement: Newton argued that particles speed up as they travel from air into a dense, transparent object, such as glass. From this source, I gather that he did argue that the light particles ...
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1answer
81 views

Specular or Diffuse Reflection - Overhead Projection

Question: What type of reflection is exhibited as light waves from an overhead projector reflect off a white projection screen and are scattered throughout a room? I said specular reflection, ...
2
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1answer
405 views

Lux and W/m2 relationship?

I am reading a bit about solar energy, and for my own curiosity, I would really like to know the insolation on my balcony. That could tell me how much a solar panel could produce. Now, I don't have ...
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1answer
422 views

Why Do My Fan Blades Produce Color When They Spin?

I've posted a short video here as a visual aid. Whenever I put my fan on Medium speed during the night time, it produces a rotating Blue and Orange color design, despite both fan blades being a white ...
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1answer
75 views

Why do we perceive a colour?

White/yellow light hits a red case, and the red color is reflected into our eyes, since other wavelengths are absorbed. My question is: since both the paint on the case and the white light have ...
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1answer
51 views

Can quanta have different energy levels? [closed]

The energy of a wave is h*f. How i imagine this is each cycle consisting of 1 quanta. I sometimes hear people say the energy of a photon is equal to h*f which makes it sound like each cycle has a ...
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2answers
47 views

Why Can You Only See Direct Light In Water From a Lighthouse

Whilst observing a lighthouse, I noticed that I could only see the cone of light reflected in the water when the lighthouse light was directly pointed at me. At all other points, I could just about ...
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1answer
43 views

Is scattering cross section determined by mass?

This is just for visible light/photon scattering. Let's say I have small spherical particles in water, if I keep the weight concentration of glass the same but change the diameter of glass sphere from ...
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2answers
150 views

Light-matter interaction and an object's appearance

I am taking a course in Computer Graphics, and the teacher said we could put materials in there main categories: mirror like glossy or specular diffuse He suggested that the law of reflection is ...
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2answers
694 views

Frequency modulation using visible light

Currently I am doing research into visible light communication from an Embedded Systems background (MSc), but I am struggling to relate the concepts of modulation of radio to visible light. I already ...
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1answer
91 views

Police laser speed detection guns

Situation Police shooting a laser device into his rearview mirror, bouncing off the oncoming car license plate. I want to know if this second surface mirror, and the symmetric system--laser gun to ...
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4answers
45 views

Can the term «shadow» pertain to anything else than light? [closed]

Can the term shadow pertain to anything else than light? Feel free to interpret this question in the widest sense possible.
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2answers
172 views

A mirror in the sky to look at past Earth

Earth reflects light from Sun into Space; are there any "mirror like" objects which reflect back to Earth this light? Has anyone been able to use this method to recover some information on how was the ...
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3answers
491 views

Why does Snell's law not factor in wavelength?

If dispersion is caused due to different wavelengths bending with different angles, how is Snell's law right in generalizing it as $\sin(i) / \sin(r)$? Or am I missing something?
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1answer
86 views

Do photons change velocity instantaneously?

Any object traveling at c is observed as traveling at c in all reference frames. When a photon travels through a vacuum at c, all reference frames observe it traveling at c. When a photon passes ...
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1answer
33 views

Does general relativity have an effect of the frequency of light? [closed]

if a lightbeam is fired from space to earth is it blueshifted? I heard this happens with special relativity but not sure if it happens with genreal relativity
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1answer
58 views

Why is it hard to make black clothes?

I've noticed that we have so-called 'black' clothes everywhere, I haven't seen so far any piece of clothes that would be really black, it's always some kind of lighter black. For instance, if you ...
4
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2answers
129 views

A light so strong it has a shadow

I have recently taken an interest in shadows. I know that in order for a shadow to exist that you must have a solid in the way of the light. My hypothesis is that there can be a light so strong, like ...
0
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1answer
538 views

If sound travels through matter what medium does light travel through? [duplicate]

So sound is a wave and is basically just vibrations, an atom vibrates causing another next to it vibrate and so on until it finally reaches our ears to become sound. If that's normally how waves ...
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0answers
65 views

What is light and how does it travel? [duplicate]

My question is: What is light, and, more specifically, how does it travel? I've been contemplating a theory that I watched on Youtube (which has no real credibility to my knowledge), the Cosmic ...
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1answer
582 views

Dark matter a medium for light propagation

Is dark matter a candidate to fill void left by luminiferous ether as a medium for light travel?
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1answer
1k views

What is the meaning of this “let there be light” joke?

A middle school teacher across the restaurant is wearing this shirt, and I certainly don't get it.
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2answers
2k views

Energy & Mass of a Photon [duplicate]

$$\text{Please read the whole question before answering}$$ Before I ask my question, I would like to say that "Yes, I do know a photon has no mass." I was helping someone here on P.SE with the ...
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1answer
55 views

What happens to light at sharp points? [closed]

At the tip of the sharp point shown, what will happen to light incident on it. This curiosity was invoked by a friend and also my childhood of watching shiny pointed swords in cartoons. Original ...