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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Why “colours” of light are given in wavelength not frequency?

If I understand correctly, when a beam of (monochromatic) light passes through media of different refractive indices, its wavelength changes but frequency remains constant. Why, then, are colours of ...
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0answers
28 views

Why does the spectrum for deuterium show a weak line at H-alpha?

I was wondering why the spectrum for deuterium shows a weak line at H-alpha, the first line in the hydrogen spectrum.
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0answers
36 views

Beating the Diffraction Limit with NSOM

I am trying to understand exactly why we can beat the diffraction limit when using near-field scanning optical microscopy (NSOM). For those who aren't familiar with NSOM, check out this article: ...
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2answers
65 views

Models of light

As far as I'm aware, there are two different (and almost contradictory) models that describe the behavior of light: light as a wave (EM), and light as a particle (QM). From what I've heard, depending ...
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1answer
60 views

What happens if light is trapped between two points?

The image can explain my question In the image light is clearly trapped.Even if the mirror absorbs energy the light is continously being added, will there be enough force to break the mirror?
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2answers
78 views

Why doesn't the Sun appear green to our eyes?

The spectrum of the Sun as seen at sea level can be seen at https://commons.wikimedia.org/wiki/File:Solar_Spectrum.png so we can see that wavelengths around green to yellow are the ones that are the ...
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3answers
191 views

Is purple in visible light?

This isn’t a duplicate. I read those pages, but those didn’t answer my questions. Please watch this. Does visible light consist of red, orange, yellow, green, cyan and blue? No purple? My definition ...
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3answers
185 views

Why most of physics is somehow related to light? [closed]

It seems that for the past 200 years, every physicist is concerned about light. For example : Newton's particle model, Young experiment, Photo-Electrict effect and Einstein's formula, Special ...
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2answers
60 views

Velocity of light

Velocity of light decreases as it enters a more optically denser medium. So how far can the velocity of light be reduced? Which object has the highest refractive index?
4
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1answer
47 views

Shadow of a ripple?

Suppose a stone is thrown into a pool of crystal clear water and its a bright sunshiny morning. You can observe a shadow of the wave in the bottom of the pool. Why does this happen? Is it due to ...
5
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1answer
120 views

What causes light to travel through a curved fountain of water?

Today I observed a tilted fountain spurting water upward (the water fell smoothly; no detectable turbulence). A colored light was shown upward into the water as it left its source. This light traveled ...
6
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1answer
806 views

Test whether a glass prevents you from getting your Vitamin D portion?

I work in an office with glass, which I believe filters the UV radiation of the sunlight. Is it possible to test if exposure to the light coming through the glass will supply Vitamin D for me as a ...
3
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1answer
112 views

Young's double slit experiment and intensity

I want to ask a question about double slit interference and the pattern that it produces on a screen (for example in Young's Experiment with a laser beam). I understand the reason that you see a ...
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2answers
125 views

Why is the spectrum of a blue flame the way it is?

In the spectrum of the blue part in a candle flame, there’s a violet emission at 432 nm due to excited CH* molecules (chemiluminescence). Why 432? Why not 400 or 500? There are emissions at 436, 475 ...
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2answers
71 views

How can shadows ever be sharp?

When I hold my hand underneath my lamp, the shadow my hand casts is crisp and sharp, meaning that the edges are well defined and not blurred. But according to Huygen's principle, shouldn't the light ...
0
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2answers
56 views

Why is there lightning where there are no clouds?

Recently my family and I went onto the balcony to observed the stars in the night sky. We started to see flashes in the sky and we realized that it was lightning (non fork lightning). I looked around ...
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4answers
4k views

Why are stars white?

That is may be a easy question, but I am not a professional. The sun is a star and when I look at the sun is usually yellow. Why stars in the night are white? I suppose is for the distance. What is ...
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1answer
53 views

How can a camera zoom & photograph the sun without damaging the lens?

I find Huge images of sun in google images, i doubt that if we zoom the sun's image by using camera, then definitely sunlight will also get intensified leads to lens damage nothing but acting like ...
0
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1answer
10 views

Saturation point of incident Light on an object

Since the color of objects depends on the parts of the visible spectrum reflected out and the remaining is absorbed; is there any maximum limit to which the absorption can take place? In other words, ...
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4answers
4k views

Is there an infinite amount of wavelengths of light? Is the EM spectrum continuous?

The electromagnetic spectrum is a continuum of wavelengths of light, and we have labels for some ranges of these and numerical measurements for many. Question: Is the EM spectrum continuous such that ...
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1answer
38 views

Red/blue shifting out of visible spectra

How fast would a white light (emitting only visible spectra) need to travel in order to red or blue shift so far its no longer visible? Are some stars completely invisible due to this effect?
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0answers
12 views

Is the link between shadows a refraction of the light? [duplicate]

When two objects in the sunlight approach, if you look at their shadows, they form a link when they are really close, is that an example of refraction? If so, is it the same as the refraction we see ...
0
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2answers
193 views

Light, being a probability wave, carries energy; does an electron wave also carry energy? If so, how?

The entity "light" behaves as a wave & particle. The wave is actually probability wave . That is, to every point in a light wave we can attach a numerical probability that a photon can be ...
3
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1answer
48 views

How to calculate the colour a human eye sees when looking at a light spectrum?

I have to do a presentation about colourants in Chemistry class (grade 12, advanced) and want to write a program that calculates and visualizes the colours of some simple molecules. What I need is ...
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2answers
431 views

Sun spectroscopy - Home experiment

We let the sun light run through a 5x3x3cm triangular glass prism and we examined the formed 'rainbow' in search of Fraunhofer lines. However, even though we looked close enough (even with a ...
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0answers
21 views

Generation of electromagnetic waves [duplicate]

I came across this while searching about generation of electromagnetic waves-Does this mean that if I vary the electric current following through a conducting wire, it will radiate electromagnetic ...
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1answer
45 views

Do photons have a spectrum like light when they are treated as waves?

If light can be treated as both a particle and a wave, are there things called infrared photons, or ultraviolet photons etc, as there are infrared waves, or ultraviolet waves? Or are photons just ...
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2answers
126 views

Are we feeling the sun's heat?

If I may summarize something I told a friend in a pub... "We don't get heat from the sun at all. Heat requires matter to move through and there's too much vacuum between the sun and us for any heat ...
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6answers
4k views

Where do photons go when they are absorbed?

The answer I usually get (and I'm paraphrasing here) is that they disappear and are instead absorbed as heat energy. But I find it hard to believe that the photon simply "disappears." Common sense ...
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2answers
163 views

The relationship between light and magnetic fields

I have two questions. Does light have a magnetic field? If not, can it be affected by other magnetic fields?
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4answers
397 views

Can we change a photon's frequency in mid-air?

Can we have a light source emitting photons in the infrared range and after, lets say, 5 meters, these photons become a photon in the x-ray range? The only way I know we can change a photon's ...
3
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2answers
110 views

Do light particle/waves have a frequency? [duplicate]

I sought the answer to the question about amplitude of light waves first, but I was actually thinking about whether the wavelength is the only property of a single quanta of light. I suppose direction ...
4
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2answers
380 views

Reflected and refracted light have same frequency as that of the incident light frequency. Why?

My text book says- When a monochromatic light is incident on a surface separating two media, the refracted and reflected light both have the same frequency as the incident frequency. Can anyone ...
8
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3answers
152 views

Why doesn't $ds^2 = 0$ imply two distinct points $p$ and $p'$ on a manifold are the same point?

Let's suppose I have a spacetime manifold $M$. Let $p$ be a point on my manifold. Now I move from $p$ to some other point $p'$. Presumably I should have moved some "distance" right? How can I speak of ...
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3answers
51 views

Frequency dependence of the speed of light in air

According to this link, the speed of light of different colors in a medium should be different. But if the refractive index of light in air is 1 then this means that the speed of light in air and ...
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0answers
33 views

Is this fine to think of light as the following? [closed]

Is light quantums (increments [photons]) of the electromagnetic waves which are synchronized by oscillations of electromagnetic fields
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5answers
201 views

White, is it a colour or absence of colours?

Our chemistry sir and we had an argument today at the lab, he says that white actually is not a colour, it is the abscence of colour, but we say that it is a colour and we gave the following point to ...
0
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1answer
73 views

How many foci does a converging or diverging lens have?

I thought this was a simple question but can't seem to find a direct answer. In ray diagrams with a converging or diverging lens, we always draw F (the focal length) on both sides of the lens. But ...
3
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1answer
120 views

How do photons carry information?

In cosmology it's frequently said that photons from the early universe carry information from that time. However, wouldn't they also carry data from later interactions? How do we differentiate ...
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0answers
99 views

Interstellar Movie: Black hole shown in the movie [duplicate]

In the interstellar movie, the black hole shown has a ring of light orbiting around it. From what I know, (correct me if I'm wrong) that light is unable to escape the gravity of the blackhole and ...
1
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1answer
124 views

How much lux does the sun emit?

I want to know how much lux the sun emits on a bright day - I don't mean when one stares directly at the sun, but rather when one walks casually outside when the sun is shinning brightly. Now the ...
2
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1answer
59 views

What material would block (reflect, appear opaque) IR light 750-850nm range, but allow visible light to pass? [closed]

I'd like to find a material, ideally a plastic, that would prevent IR light from passing , but appear as transparent as possible to visible light. I've sampled some plascolite products and they work, ...
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2answers
338 views

Why does a circle of light appear when I shine a laser pointer at a wire? [duplicate]

When I point a laser at a wire , a circle of light appears on a wall behind it . why this happens. What is the circle of light and why does it appear? Could anyone give some tips on what I should ...
3
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3answers
504 views

Why are solar panels blue, rather than black, when black absorbs more light?

This is an image of a solar panel array, courtesy of Wikipedia. Some of these look rather black, but most of them are blue. As far as I know, solar panels work by absorbing "light energy", and ...
0
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1answer
24 views

How does the flow of photons (qty/s) vary across the spectrum? (In everyday life)

Humans see only a narrow band of light wavelengths. Many animals see much deeper into infrared. Maybe one clue to explain why we don't see IR naturally, has to do with the light intensity as a ...
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2answers
42 views

What should be the width of the slit in single slit diffraction experiment?

What should be the width of the slit in single slit diffraction experiment? If the wavelength is taken lambda while doing experiment.
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0answers
28 views

How is the formation of the first atoms related to the cosmic microwave background? [duplicate]

Common atoms formed when the universe finally got cool enough for electrons to bind with atomic nuclei around the year 380,000. From what I understand this shift in state from plasma to discrete atoms ...
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0answers
19 views

Making sense of sinogram of perspex block in air

I'm confused trying to visualize what happened exactly during this experiment: Setup with a laser and a photo diode on the opposite side. A perspex block (2x2cm) in between. Take 200 measurements ...
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3answers
126 views

How are photons made?

I mean in manufacturing a bicycle we know how to "ensemble" a bicycle, what actions and "assembly of parts". So what steps are needed for make a photon? Also is there a limit on how many photons for ...
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0answers
59 views

Reflection and refraction of light [duplicate]

When a light ray strikes an interface a part of it gets reflected, a part of it gets absorbed while another part gets refracted. Why does light reflect? Why does it refract?