Questions tagged [visible-light]

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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How can the magnetic $B$-field of a photon or light wave be directly compared to the electric $E$-field if the units are different? (Tesla vs. V/m)

I know that the electric field of an electromagnetic wave has the strength (or intensity?) of the magnetic field times the speed if light $c$. (E = B × c)... But, the units are not quite the same (I ...
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What is the difference between internal reflection and total internal reflection? What exactly happens during rainbow formation? [closed]

heard about the concept of internal reflection on a rainbow formation video - it was said that internal reflection is like "the smaller brother" of TIR. Found no article regarding this so ...
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3D information from shadows

I was holding a 1 inch diameter pipe recently on a sunny morning. I noticed that the turning the pole at various orientations changed the shadow on the ground. The closer portion of the pipe to the ...
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How much UVA and UVB is blocked by shadow or being indoors?

I could not find a clear answer online so I though to try this forum instead. I did find answers on how different types of glass can block different degrees of UVA and UVB. But I was wondering, if I ...
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Does any colour appear white to our eyes if its emitted power is extremely large?

let's consider an ideal monocromatic source (for instance red) and let's assume you can regulate its emitted power without compromising its spectral "finesse". Start from 0 emitted W/sr. It ...
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How to calculate luminance, given a light source's luminous intensity?

For example, let's suppose I have $2.5$ mm diameter LED with a diffuse lens; it has luminous intensity of $2.0$ cd. Let's say it has viewing angle of 120 degrees and I'm viewing it head on. How would ...
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What do the CIE Standard Illuminants SPDs represent?

The CIE publishes the relative SPD for standard illuminants. I was curious what photometric quantity it represents i.e. radiance or irradiance or something else. I was reading the "Intro the ...
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How to approximate a light source as a point source of light?

A point source of light is "single identifiable localised source of something" (from Wikipedia). However, there are no true point sources of light in nature, since no object is as small as a ...
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Which is the real reason for why we don't see light interference patterns?

There are many questions like mine in the web, but think I cannot fully understand it. Let's look at this question. The first answer states that we cannot see light interference patterns because most ...
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Line widths of Ne spectral lamp

I need to know the line widths (FWHM) of spectral lines of a Ne spectral lamp. There is a lot of information about the lines' center on the internet, but I couldn't find anything relevant or ...
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How much energy holds the full visible light spectrum? Same to heat absorbed by back color?

I would love to know how much energy a black body absorbs from the visible light. In the following site we can calculate the eV of a given wavelength, but if I'd like to know the sum of eV for the ...
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How do lasers work if the phase shift from reflection is 180 degrees?

I am having a hard time wrapping my head around the phase shift that is imposed by reflection. I'm specifically thinking about things like visible light of off mirrors or RF reflecting off of silver, ...
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What is the energy difference between the 3d 4s valence subshells of iron (and copper)?

In gold, for example, the energy difference between the 5d 6s valence subshells is ≈ 2.7 eV (that's why it has color). But what about the 3d 4s subshells of iron and copper? What are their energy ...
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Why is it that you can see transparent or translucent objects and see what is behind them at the same time?

For example, a cup with water in it is seen by us. We can see the cup being there, and yet also see the distorted image of whatever is behind the cup. Furthermore, we can clearly see translucent ...
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How can the intensity of the center of Arago's spot be calculated?

I am currently working on measuring the relationship between the diameter of the sphere and the intensity of the center bright point of the shadow with Arago's spot. I have been researching with ...
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Does the manipulation of the Fresnel number and light intensity work?

I am currently a high schooler and am trying to find the intensity of the bright point in Arago's spot. I am trying to find some manipulation of equations to hopefully gather the intensity of the ...
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How does RGB really work with subpixels?

first off, I’d really appreciate any help. I have googled relentlessly to try to understand this, but I’m too stupid to fathom it. Please attempt to explain this to me in plain English if you can. I ...
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Scattering Of Light- How does it happen with Sun and Earth?

Since the Distance of Light from the Sun in the Horizon Part is High, then the Red light is scattered more. But what happens if the earth rotates on the axis? the Distance will be more but at the same ...
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Does radiant flux depend on solid angle?

I learned from various sources (e.g. Wikipedia) that the radiant flux $\Phi$ is the radiant energy emitted, reflected, transmitted, or received per unit time and is defined by: $$\Phi(\mathbf{x},t) = {...
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What do we actually mean when we say "light"?

light is an electromagnetic wave , but can we say all EM wave are light? eg. infrared radiation , uv radiation ... can we say these as light?
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Feynman's view about light

Professor Feynman, in his “QED: The strange theory of light and matter”, states at page 15: “I want to emphasize that light comes in this form - particles. It is very important to know that light ...
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Does electromagnetic waves (light) bend spacetime like mass? [duplicate]

we know that mass bends space time does electomagnetic waves bend space time? because EM waves dosent have mass. we also know that higgs field and higgs boson is responsible for mass of photon is zero ...
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Can anyone explain this peculiar optical phenomina?

I have been a passenger in a car driving at night in cambodia, I have noticed that the lights from the cars appear to be lines instead of a circular symetric glow. I know my eyes have the condition ...
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Isotropic speed of light verification [duplicate]

I have an idea for checking the isotropic speed of light in all directions that, as far as I can tell, does not involve clock synchronisation or mirrors or so called mechanical rigid bodies or ...
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Can I really see what is on the opposite side of a black hole?

This question is only about objects outside the event horizon. Both the observer and the object are just outside the event horizon. I have read this question: An observer can see the back side of the ...
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Why do things have colour? (reflect certain wavelengths of light)

Why does something like an apple, which has many different types of atoms and molecules in different arrangements put together in a complex manner, reflect only certain wavelengths of light, instead ...
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1 answer
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Can someone explain the Fresnal diffraction simply? [closed]

I have been researching and found multiple equations. There are ones for the Arago's spot, fresnel number, fresnel diffraction, fresnel integral. They often lead to other wave behaviors which confuses ...
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Light curve of supernove: rise of LC

I have a question concerning the LC of SNe. First of all we have a huge energy deposited into the core of a star ad as a result we have a huge shockwave that develops, that heats and accelerates the ...
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What unit should I use to measure the light intensity of aragos spot

I am trying to measure the relationship with the radius and its effect on the light intensity of Arago's spot. I plan to use a camera or a light meter but I am not sure what unit to use in my ...
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1 answer
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I'd like to understand the way suspended clay and silt particles in glacial lakes scatter blue and green light

My current understanding is: this can be described mainly as Rayleigh scattering: Incoming white light from the sun is scattered by particles with resonances in certain wavelengths. The wavelengths ...
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Reflectance spectrum of white notebook paper

What is the reflectance spectrum of a high pile of white notebook paper? An answering article (for one sheet?!) has been linked in this question, but the article isn't available anymore, I don't have ...
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Converting light into heat/movement, reflection vs absorption

at school we had a small device in a glass dome it had 4 plates every plate was blackened on one side and silver colored on the other side. when the sun did shine on one side of it, it would start to ...
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Speed of light in non-vacuum mediun for different wavelengths

I understand that the speed of light for different wavelengths is different in a non-vacuum. Many of the explanations point to how different photons interact differently with the atoms in the material....
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What percentage of sunlight isn't scattered by the atmosphere?

What percentage of sunlight isn't scattered by the atmosphere and instead will arrive at your eyes directly from the sun. It's been aksed here before but a proper answer hasn't been given. I was ...
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Difference between Earth's surface area seen from ISS and the theoretical area if light refraction is neglected

What is the difference between Earth's surface area seen from ISS and the theoretical area if light refraction is neglected? I watched a video telling that it is not possible to know why a great ...
1 vote
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What causes light passing through a hole to change direction?

On diagrams showing light passing through a hole, the wave of light appears to change direction when it emerges from the hole. What causes that change of direction? Is it maybe the walls of the hole ...
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What tells to a point that the eletromagnetic field has changed? [closed]

I'm taking classes in electromagnetism and studying the physics of light. My professor (and everyone says) that a charged body emits light when it's accelerated. Thinking about, I got a problem. ...
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Not seeing the expected rainbow

I was expecting to see a rainbow inside the house from the sunlight coming through the window, at least when the sun is shining right through. Why wouldn't it? But we just get the yellowish color of ...
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Is it true to say no refraction takes place when a ray comes along normal drawn to interface?

Many books and websites in our country say that there are two conditions for no refraction of light: If index of Refraction of media on both sides is same. If the ray of light falls normally on the ...
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What are the sources of electric and magnetic fields that produce lights?

Electromagnetic waves are formed as a consequence of the interference of electric and magnetic fields. I wonder where are these fields coming from that form the light? Does the fields have to be ...
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Why do dark objects absorb visible light but only emit infrared radiation?

What is it about the molecular structure of dark coloured objects that means they absorb most of the visible light that falls on them, but radiate infrared? Naively I would think that if a molecule ...
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Questions regarding light being depicted as a sine wave [duplicate]

Light waves are often depicted as sine waves... Why is it so? What's actually waving? And what does the sine wave signify and represent? What does wavelength of light mean/signify? and how is it ...
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How could 19th century people know light is electromagnetic waves?

From Maxwell's equation, we can find out that certain waves exist. However, it's unclear to me why 19th-century people thought that what they had called light is a wave. As far as I know, 19th-century ...
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Why the sunset is red and a possible experiment?

Before downvoting: I have read some of the answers and will cite them as well. Not trying to debunk physics or create conspiracies. I love physics but I don't understand it. Background This is more or ...
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How saturated are colors in a real rainbow?

Some time ago, just starting out at a photographic company, I asked why essentially all media depictions of rainbows look fake. A color-theory expert there asked how saturated I thought rainbow colors ...
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Why don't our eyes get overexposed like a camera with too slow a shutter speed?

Perhaps I'm just not understanding the exact mechanism of how light interacts with our eyes and is interpreted as an image, but for cameras light goes through the lens and hits the image sensor/film ...
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How are sunglasses only reflective on one side?

Sunglasses can be colored on one side, and dark on the other? Why aren’t both sides either dark or both sides colored. I figured it worked like a one way mirror - but after holding both sides up to ...
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A large signal bandwidth for a small spread frequencies in optical communication

I am undertaking a new module in optical communications and have been provided some notes over the summer to be better prepared for classes. However, I am confused by some of the content in the notes ...
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Why do raindrops look like sticks?

I always thought that raindrops look like this emoji 💧. But today, I shot it in slow-mo (see on YouTube), and they look more like sticks. Was it some light effect of my camera, or do they really look ...
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Why does my glossy blue guitar reflect different color images on my phone, but reflects white from a gelled camera flash

I have a blue glossy guitar that I was trying to photograph for product photography practice. I wanted to have a pink rim light on it, so I angled the flash appropriately and put a pink gel on it. ...

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