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 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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Try this method to calculate the speed of light [duplicate]

The speed of light as we know by today is 299,792,458m\s. But that is a two-way speed of light. Light first striking a mirror and then reflected back. No one has actually ever measured a one-way speed ...
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Is there any old/new research talking about the possible role of ozone on (theoretical) invisibility cloaking devices? [closed]

I really don't know if I should be asking this here or in Worldbuilding. I've heard a few times about old school sci-fi stories about invisibility cloaking devices that specifically suggested that &...
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How to know if one-way speed of light is different from other? [duplicate]

I'll be using Veritasium's idea of Mars and Earth, so if you know, you know. We start by measuring the time it will take light to travel from Earth to Mars and for that we will use the simple formula, ...
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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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Is the speed of light accurate? [duplicate]

Speed of Light As we know by today that the speed of light is exactly 299,792,458m\s. French physicist Hippolyte Fizeau is credited with making the first ...
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4 answers
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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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Diffrence between thermionic emission and photoelectric emission

Thermionic emission involves heat energy to excite the electron and remove it. In the photoelectric effect, a beam of light is involved. As per my understanding heat and photons, both are energy. Heat ...
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Is specific rotation a constant? [closed]

This is the formula for Specific Rotation of a solution. Can I rearrange to make c as the subject and then say that theta is proportional to c? If not, is there any other way in which I could relate ...
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Is it possible to make an object transparent? [closed]

If you were to push the electrons from an object onto a valence band, it would need an energy of 5.4 eV to push it back into the conduction band. Would that make an object transparent since visible ...
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Does the field vector rotate clockwise for right circular polarization when viewed from behind the source of the wave?

Descriptions and images of right or left circular polarization do differ based on a viewpoint being either behind or in front of the wave source. Furthermore, I see pictorial representations that do ...
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Would be possible to notice the light distorntion of a glass sphere inside a panel/cube of epoxy or water glass?

Let's say we put a sphere of glass inside a cube/panel made of transparent/semi-transparent epoxy or water glass (sodium silicate), would the distortion of light that glass spheres has on visible ...
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How much energy/heat is absorbed in theory by different colors?

I would like to know how much heat captures a given color body or surface from visible light (not from IR). I understand that it would be the integral of the whole visible range minus integral of, i.e....
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Is the polarity of light maintained after reflection from a dielectric surface?

If I send an artificial light source’s light through a linear polarizer, and that light reflects off a dielectric surface at a narrow angle, is the polarization angle maintained (in this case its ...
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Why do people say that blue light is damaging to the eyes? [closed]

It's easy to find claims that blue light (e.g., from computer screens) is damaging to the eyes. For example, here is some discussion of the topic. Is there any physical mechanism by which blue (not ...
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How can we send radar to Venus and reflect it back on earth?

Question How is it possible to send laser light to Venus and reflect it back on earth? I believe there is no artificial reflection material e.g. mirror on Venus. Background Veritasium How One ...
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Is there a difference in Earth's magnetic field between day and night?

Is there a difference in Earth's magnetic field between day and night? Magnetic Field
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Why does the light from stars / satellites tremble? [duplicate]

Clear Sky. 1 ---> Light from stars visible. 2 ---> Light from satellites visible. 3 ---> Light from airplanes (passing by) visible. Apart from the change in color, the light from 1 and ...
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Why does sound follow the laws of reflection, I read in Feynman lectures that Q mech is the real reason for Fermat's principle but why sound follows?

You can also check out science asylum video on how mirrors work, he explains similar thing as written in Feynman lectures. But I do not understand why sound should follow the same thing
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Why is there so much polarized light in the atmosphere?

I thought to look into the environment for the inspirations, and what could be so easily accessible as a photogenic sensor (a camera)? The diffraction from the lens was the experimental proof for the ...
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Crossing lasers, information loss and the human eye query

Let us set up 2 crossing lasers. Laser Source A passes through a projector slide of the Mona Lisa then through a lens to expand and project on screen A. Laser Source B passes through a projector slide ...
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How reflection takes place in colorless particles like water molecules?

How can we see any color? well, the reflection of light of different colors takes place. but what happens in colorless particles like a water molecule. how reflection takes place. how can I see water? ...
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Improve Spectrometer SNR

I am trying to perform optical emission spectroscopy but I have very low light intensity. Without increasing the intensity, can I improve the SNR somehow? I am already close to the saturation point of ...
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1 vote
1 answer
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Radiation pressure at a oblique surface

I am doing a problem that asks the radiation pressure of a beam of light on a oblique surface. The problem says: A laser beam of intensity I reflects from a flat, totally reflecting surface of area A, ...
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3 votes
1 answer
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How can we still see the CMB? [duplicate]

May seem stupid but i cant wrap my head around it. if a star explodes we eventually see it when the light gets here. but once its got here we see the event and the star is now gone, we cant see it ...
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What range of light on the electromagnetic spectrum are produced by the de-excitation of electrons?

When an electron moves from an excited state to its ground state, a photon is emitted, which is the source of light. However, I know that the highest energy form of light, gamma rays, are produced ...
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Why do some anti-reflective (or anti-glare) lenses use layers of materials with alternately very high and very low refractive indices?

Some specials lenses like this (or coatings on them) try to minimize the refractive index, or the change thereof, or at least make the change very gradual. But others apparently do the exact opposite, ...
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Why gold is yellowish? [closed]

This question -- Why are most metals gray/silver? -- is partly about why gold is yellowish. The most popular answer (and thus I assume the right one) -- https://physics.stackexchange.com/a/72412/...
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Shapiro time delay

How do we know for sure that the Shapiro time delay effect is as a result of curved space time and not simply the photons slowing down.
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What if water had negative index of refraction

I was reading a book of mine that states that if water had a negative index of refraction then we'd see fish suspended in air. Why? Should not we see still it in water but far away respect to its real ...
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Light and Special Relativity

If an object is in motion that means time slows down for the observer in motion. So if there is a planet that is 1 billion light years away that is moving away from us does that mean we are seeing ...
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What is the wavelength of red light in vacuum?

According to Wikipedia, It has a dominant wavelength of approximately 625–740 nanometres. However, I'm not sure in which medium this wavelength was measured. Was this wavelength measured in a vacuum?...
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Photons implying particle nature of light [duplicate]

We know that in the photoelectric effect experiment, the particle nature of light was proved via photons. Again, we know that photon has energy $h\nu$ where $\nu$ stands for wavelength. After ...
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White full moon reflected orange-red light off of Atlantic Ocean surface. Why is this?

I was flying over the Atlantic at night in near complete darkness. There was a white, bright full moon. It’s moonglade (the light reflected off the waters surface) was a orange-red color and not white....
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Water trick, explanation needed

So I encountered this video of glass changing colors when placed in water and outside of it. How is it explained by physics? Video: Guy puts glass on table where is no water, and the glass appears to ...
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1 vote
1 answer
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Did Huygens understand light to be a transverse wave or a longitudinal wave? [closed]

We have this source that claims Huygens "assumed light to be longitudinal", which contradicts this source which claims "Huygens believed that light was made up of waves vibrating up and ...
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1 vote
2 answers
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Why do we draw two rays from a same point on an object during image formation?

When we draw ray diagrams for image formation of an object through refraction or reflection we generally draw two rays emerging from a common point on the given object, by our nature of thinking (or) ...
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1 answer
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Non-dispersive mediums for light

Apart from the vacuum are there other mediums for which light velocity does not depend on frequency?
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Reflection of light on a colorless material. What happens on atomic level?

I try to understand reflection explained with photons that are interacting with molecules on atomic level. For this I would like to start with an example and ask the question based on this: Say I have ...
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1 vote
1 answer
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Why does the boundary shows different colors between black and white regions on a projector screen?

Original Question: My friend took a picture of his screen from an angle (please see the attached picture) and found that the colors of the boundaries from white to black and ones from black to white ...
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15 votes
11 answers
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Can you actually stand inside a rainbow? I see people claiming you can

I have been thinking about this for ages and it has been driving me crazy. I was convinced that rainbows are always complete circles that appear to be arcs because they cross the horizon. Then, I saw ...
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Is it possible to get a material which yellow in normal light and doesn't reflect spectral yellow?

Imagine an object which reflects only green and red spectral colors. In normal light, it should appear yellow. But when we light up this object by spectral yellow color, it should appear dark, because ...
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Does destructive interference of photons destroy energy? [duplicate]

I am wondering about if two light beams comes in opposite phases exactly against each other, destructive interference will happen. From what I have found on the internet many say that energy is not ...
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Absorption spectrum of white light of the Sun

When some photons in the white light from the sun are absorbed, this means some wavelengths will be missing, so how does that light still appear 'white', although some of its constituents are missing?
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Specular and diffuse reflection at the same time

if we know that tomatoes absorb all the light and reflect the red diffusely, how can we see the reflection of all the light specularly at the shinnig point? there isnt an absorption of other colors at ...
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Extent of scattering of light

I am absolutely no expert in physics but I really want this question answered and the reputation of the forum is good. So my question is if I have a magnifying glass, for example, it can fix the light ...
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How do we define a color? [duplicate]

Is Black a color or just the absence of others colors/light . What actually constituents colors? How do we define if something is a color or not?
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3 answers
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Are radiance and luminance really independent of distance to observer?

Recently, I learned that apparently both radiance and luminance are independent of the distance between the light emitting object and the observer. The reasoning was that although the radiant/...
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How come $P=Fv$ applies to light? [duplicate]

I was asked the following question in a physics worksheet: A $2.0 \,\mathrm{mW}$ laser is shone onto a metal plate. The cross-sectional area of the beam is $4.0\times 10^{-6} \, \mathrm m^2$. Assume ...
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