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.

learn more… | top users | synonyms (2)

1
vote
3answers
62 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 ...
66
votes
2answers
3k 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 ...
1
vote
2answers
120 views

Does the formula $ \theta = \frac{v}{c} $ to find out deflection of light make sense?

I read in reliable sites that GR and classical physics calculate the angle of deflection in the same manner. The formula is almost identical: $$\theta = \frac{4GM}{c^2*r} \rightarrow \frac{4GM}{c*r} = ...
4
votes
1answer
91 views

Is that a result of thin-film interference?

Several years ago, I was laying on my bed and had a CD shaped transparent plastic disk (which was covering a 100 CD stack), basically a transparent CD. I don't know why but I took my phone and took a ...
5
votes
2answers
322 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 ...
0
votes
2answers
56 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 ...
0
votes
0answers
13 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 ...
17
votes
3answers
679 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 ...
1
vote
1answer
27 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 ...
30
votes
4answers
6k 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. ...
0
votes
2answers
47 views

Wavelength of blue filtered light

Does blue filtered white light have a certain wavelength, or is this highly dependent on the filter and source of light?
0
votes
0answers
9 views

Measure rolling shutter severity of image sensor scientifically [closed]

Is there a way how to measure the "severity" of the rolling shutter (RS) effect of a given image sensor? I guess such a method would require to take a picture of something that can be measured, ...
2
votes
3answers
56 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 ...
40
votes
6answers
5k 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 ...
0
votes
0answers
33 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 ...
0
votes
1answer
52 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 ...
1
vote
0answers
11 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 ...
0
votes
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 ...
2
votes
1answer
482 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?
2
votes
2answers
294 views

Why can I split white light into separate colors with my eyes

I was sitting in a meeting at work today. When I looked up there was a projector facing the rear wall letting out a very bright white light (the projection). When I look right at it, all I could ...
3
votes
1answer
21 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 ...
0
votes
2answers
43 views

Resolution of the Eye-Light Rays and Diffraction

Please look at the problem. The problem is solved for me. However, I don't understand why the angle alpha is considered to stay constant when the rays go through the lens. The ray along the ...
0
votes
1answer
33 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 ...
3
votes
2answers
63 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 ...
5
votes
3answers
3k views

Real and imaginary parts of dielectric constant vs refractive index?

So for a complex dielectric constant $\epsilon = \epsilon_a + i\epsilon_b$, the wave vector and index of refraction are related to it through $k = \frac{\omega}{c}n$ and $n = \sqrt{\frac{\mu ...
2
votes
1answer
28 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, ...
8
votes
1answer
373 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 ...
1
vote
1answer
64 views

Helicopter blades

Why do the propellers on helicopter appear to be so slow when the propellers is going at full speed? Can you please explain this particular optical illusion to me?
2
votes
1answer
38 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 ...
9
votes
2answers
169 views

Which of these theories on why light slows in media are true?

This question is similar to previously asked questions, but the responses to them are confusing and I think it may be better covered by listing out all the potential answers for clarity. It's a ...
0
votes
1answer
59 views

Given two surfaces, one that absorbs light and the other that reflects it, will there be a signficant temperature difference?

My likely wrong understanding of light is this: By some way the molecules are structured, a photon hits an atom or a structure, is absorbed, then re-emitted and it's that photon wavelength that I see ...
0
votes
1answer
54 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 ...
1
vote
1answer
137 views

photon polarization, uncertainty in Energy

A beam of red light is sent along the $z$ axis through a polaroid filter that passes only $x$ polarized light. The beam is initially polarized at $30$°, and the total energy is $10$ Joules. Estimate ...
2
votes
0answers
41 views

What causes the lines in these photos of a flourescent tube?

I was taking pictures of a flourescent tube using a Moto G 2013 when I noticed these evenly spaced lines as I got closer to it. The distance between the lines reduced as I got closer to the tube. ...
-1
votes
1answer
37 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 ...
0
votes
2answers
26 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 ...
4
votes
2answers
72 views

What is the physical structure of light?

Conceptually, I understand what light is, but I don't know what a photon would "look like" if it could be frozen in space/time. For instance, the notion of amplitude seems to be absent when discussing ...
5
votes
2answers
253 views

Why must an integrating sphere be a sphere?

Why must an integrating sphere be a sphere? Why can't it be an integrating cube? What is the difference? Could I use a cube to measure total illuminance like an integrating sphere does?
0
votes
2answers
65 views

Light-Matter Interaction and 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 ...
-1
votes
1answer
1k views

Frequency Of Light

I am confused on few topics... What is meant by "Frequency of Light"? Does the Photon(s) vibrate, that is known as its frequency? If the Photons vibrate, then they have a specific frequency, then ...
0
votes
1answer
29 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 ...
7
votes
2answers
486 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 ...
1
vote
1answer
69 views

What does the size of an object have to do with it's color?

Stephen Hawking mentions in his book 'A Brief History of Time' that quarks are much smaller than the wavelength of visible light so they do not have any color in the normal sense. What exactly does ...
1
vote
1answer
61 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 ...
0
votes
4answers
43 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.
2
votes
1answer
74 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 ...
4
votes
3answers
370 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?
2
votes
1answer
37 views

Optical fibre modes and intensity pattern

I shine laser line in front of one side of multimode optical fibre.Light coming out of other side is projected into wall.Whether the intensity pattern seen on wall is same as the mode of propagation ...
1
vote
1answer
73 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 ...
0
votes
1answer
102 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 ...