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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Why at sunset the sky looks like a rainbow?

Why at sunset the sky looks like a rainbow?The higher part looks blue then as we look lower and lower we see white, yellow, orange and finaly red...as in the picture. Why the red light is so much ...
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Why does light interact with mass? [closed]

If light is just a disturbance in the electromagnetic field, then why does it interact with mass?
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Scattering of blue wavelength and red wavelength in our atmosphere

I've read the reason sky appears blue is because blue wavelength is being scattered by the gas molecules, dust particles etc. Thus, because of this scattering, we are basically being bombarded with ...
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3answers
149 views

Can photons only exist in the state of motion?

Photons are known to travel at a speed of 299 792 458 m / s in vacuum. Photons can be absorbed, or absorbed and re-emitted by matter. They slow down to 225,000,000 m/s in water with a refractive idex ...
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Why do my white shoelaces get blue when exposed to UV?

My shoes and shoelaces are both white. But when there is a UV light only my shoelaces appeared in a different colour. What is the reason?
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Blue laser scattering in the atmosphere: At what distance the laser source is no more seen as a pointlike source due to Rayleigh scattering?

Blue laser scattering in the atmosphere: At what distance the laser source is no more seen as a pointlike source due to Rayleigh scattering? Does this distance depend of the intensity of the laser ...
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Why the blue component of the moonlight is less scattered in Earth's atmosphere than the sunlight?

Why the blue component of the moonlight is less scattered in Earth's atmosphere than the sunlight? So when rising one of them looks yellow and the other red. Is this only matter of their brightness ...
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How to define the electric and magnetic fields of an EM Wave in a vacuum?

After learning about the production and propagation of electromagnetic waves I've become a bit stuck in my understanding of how to think of the electric and magnetic fields that make up an ...
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1answer
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Does a white surface reflect more light than a mirror?

I read that a (sufficiently) white surface reflects more (visible) light than a mirror. Is that true? And if yes, why?
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Wien's law and colors

I know there are a Wien's law for frequency and one for wavelenght, but I'm wondering which one is the most accurate when it comes to our perception of colors. For instance for the Sun, the Plank ...
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If a polarized light wave is indistinguishable from its original self after being flipped 180°, why doesn't a photon have a spin of two?

The spin of a photon has a counterpart in classical physics, it's polarization, right? And if you spin a polarized light wave by 180°, (or pi radians), it is now the same as before, correct? So why ...
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Why a moving light source shows as several discrete sources instead of a gradient

I have a device with 4 small leds. Like: • • • • If at dark I move the device I would have expected to see a gradient of continuous light. Like: ...
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How much does light curve due to gravity compared to what Newtonian mechanics predicts [duplicate]

I've heard that it curves twice as much is this correct?
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Using light as an energy condenser

If I created a sphere with the internal surface perfectly mirrored and shone an intense light into it from a small aperture, what would happen to all the photons being accumulated? If I then at some ...
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1answer
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How would the focal length of a convex lens change if it is submerged in a liquid of higher optical density? [closed]

We know that when a convex glass lens is submerged under water, it's focal length increases- As refractive index of the pair of media reduces and the light rays deviate less to meet the principal axis ...
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What are the physical processes involved in feeling warm from the sunlight?

Suppose a human is lying on a beach. He/she starts to feel warm after exposing his/her skin to the sunlight. I assume that feeling is due to the ability of the human body of "measuring" the ...
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Source of light [closed]

Is this statement true" Chair is a source of light". We know that there are two types of source of light(1) Primary source of light ( like bulb, candle) (2) secondary source of light ( like ...
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4answers
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A Light is shone out the side window of a spaceship ( moving close to light speed ), will the light still travel at the speed of light in the B axis?

A Light ( or laser ) is shone out of the side window of a spaceship ( which is moving as close to the speed of light as possible ), WILL THE LIGHT STILL TRAVEL AT THE SPEED OF LIGHT IN THE B AXIS ON ...
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If a light beam is sent tangent across earth would it curve at 9.8 $\rm m/s^2$? [closed]

Just to see if my understanding of the curvature of light is correct.
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How does "light" light up a room?

QUESTION: Does light beams (example: from a bulb in a dark room) hitting a wall split up to form more beams, resulting in the room lightning up? I am generally curious on how light can bright up a ...
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3answers
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What is the Time $t$ when a Beam of Light travels Infinite distance? [closed]

Now, by the Picture we know that $D=-1/12$ by $1+2+3+4+...=-1/12$ Therefore, By Speed$=D/t$ 3*10^8=(-1/12)/t Therefore, Time ‘t’=-1/(12 * 3 * 10^8) t=-1/(36*10^8) How is this Possible? Please Note ...
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2answers
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Sunlight colour

I know the sunlight is white colour and appears yellow because of dispersion through atmosphere. I want to know why this yellow light when pass through prism divided into 7 colours.
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What is light, a wave or a particle or A wave-particle? [duplicate]

What is light? And how do we know that light is an electromagnetic wave? I asked my teacher and he said that when you place a compass in light's path, the needle of the compass rotates. Which I think ...
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Why does the Sun appear white through clouds?

Why does the Sun appear white through clouds? It seems there should not be any absorption of, say, the reddish component, as this would not produce a white colour. So what is going on? Am I right that ...
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1answer
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Intuition behind Huygens-Fresnel formula

I'm currently studying Optics, and I stumbled upon another alternative way in which to derive the Intensity Distribution of light through a slit. My question is, why does the formula work. $U(r_{0}) \...
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1answer
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Are there any objects that are transparent to humans but opaque to cats and vice-versa? [closed]

What makes an object transparent or opaque is complicated as far as I know but depends on which wavelengths the observer can see. Since cats can see different wavelengths than us humans, are there ...
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2answers
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Why the dipole interaction term in the Hamiltonian has all diagonal elements to be zero in the energy eigenbasis?

I have been studying the semi-classical light matter interaction from the book, "Light matter interaction" by Weiner and Ho. They have defined the total Hamiltonian of a two level atom ...
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7answers
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Do the "colors" live in a 3-dimensional vector space? [closed]

Do the "colors" form a 3-dimensional vector space? Colors are just different frequencies of electromagnetic lights, from the low frequency (infra-red, red) to the high frequency (blue, ...
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1answer
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Can light wrap onto itself and become stationary? [closed]

This is possibly pure nonsense. I read somewhere particles interact with themselves and this makes calculation complicated. No idea where I read it but I remember reading it. I wonder if light can be ...
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3answers
70 views

Can a very fast centrifuge affect the path of a light beam?

I am thinking the answer is "no" since you can't see time dilation (I have read) in a centrifuge. But why would a light beam not be bent by what is felt like gravity to someone inside the ...
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Need help in clarifying my understanding regarding absorption and emission spectrum

In absorption spectrum . So , what happens here is that when white light is passed through a gas. The photons of the white light are absorbed by the electron in the gas. This means that the electron ...
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1answer
83 views

Is the light emitted by an incandescent bulb monochromatic?

Why does an incandescent bulb emit yellow light, and is this light monochromatic? Also, are the different coloured lights produced by coloured disco/party lights monochromatic or not?
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How wide a field would an LED emitting 81,000 lumen placed at a 45 degree angle create at a distance of half a mile? And what intensity at distance?

Trying to answer question related to light pollution for 45 degree "wing-up" parking lot lights (type IV) in the particular situation where the lights are located in a valley between ...
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1answer
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How can glass be destroyed by red light?

I was reading this answer and follow up comments: https://physics.stackexchange.com/a/623227/230132 Alessandro says red light can damage a piece of glass if its intensity is sufficient. I assumed ...
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Position of Central Maxima due to multiple path differences in YDSE

In a YDSE experiment, the apparatus is immersed in a liquid of refractive index μ1. And also one of the slits (S2) is covered with a transparent slab of refractive ...
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2answers
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If we can see the light reflected off objects, why can't we "see" light? [duplicate]

It's said that light is invisible because photons don't strike each other, then why we do see the reflected light from other objects?
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1answer
29 views

Do all radioactive isotopes and compounds exhibit photoluminesce?

I have an antique item - colored in a florescent yellow, which may be comprised of radioactive pigment like Uranium Oxide or other radionuclides I haven't a Geiger counter, but I already shined a UV ...
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1answer
31 views

How bright would the surface of each planet be?

At night when there is no moon in the sky, it is dark, you can not see your surroundings. If I were to stand on Pluto, could I see my surroundings? Would being on pluto at day be like night on earth ...
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1answer
64 views

Is there a limit to how much light can pass through glass?

Let’s say I have a one cubic centimeter of glass. Without going into the details, we know that light passes through this glass with the help of the glass. The glass facilitates light’s transmission ...
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1answer
154 views

What are so-called opposite colors?

Colors are said to be electromagnetic frequencies. How is this compatible with the notion of color opponency, or opposite colors, since those frequencies form a single dimension?
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2answers
124 views

Why do different colors appear to move at different rates when I shift my head while wearing eyeglasses?

I have significant nearsightedness (and some astigmatism), but see just fine with eyeglasses. One phenomenon I've noticed is that when I shift my head side to side or up and down while keeping my ...
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Is this general relativity diagram correct?

The following diagram is presented in my professor's general relativity notes: The diagram comes along with a description of the relativistic bending of light, and the explanation is somewhat clear, ...
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108 views

In sunlight a shadow looks darker relative to the sunlight, but is it actually brighter than when there is cloud cover?

Considering the same point in a shadow on the ground, how does the incident light level vary when there's cloud cover diffusing the sunlight compared to no cloud cover? In sunlight a shadow looks ...
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49 views

Gravitational light bending

I'm trying to follow the next proof referred to the bending of light in a gravitational field (calculated using exclusively the Einstein's equivalence principle). Suppose you have an observer in an ...
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2answers
235 views

Does diffusion happens for the photons from higher concentration to lower concentration

I understand that it is the random motion of the molecules that causes them to move from an area of high concentration to an area with a lower concentration and the diffusion will continue until the ...
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3answers
412 views

What happens to light as it enters a denser medium?

I am a first year undergrad student doing optometry (never done any physics before in my life :( ). I got a question asking what happens when light enters a denser medium. I was told that the ...
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37 views

Constructive interference in single slit diffraction

Double slit diffraction seems to be easier to understand than single slit diffraction, in which the single slit are thought to be wider, therefore multiple sources of semi circular waves are present ...
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1answer
25 views

Why do Photo diodes in Computer Mouses don't generate electricity when receiving light? [closed]

I had been researching about photovoltaic cells recently for a science project. In my researches,I stumbled upon photovoltaic cells,silicons,solar cells,and photodiodes. Photodiodes and Solar panels ...
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5answers
132 views

Is it a postulate that light travels on a geodesics?

In arbitrary spacetime, light travels on geodesics. Is this a postulate or can it be derived from a more fundamental principle?
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51 views

How many ways are there for light (electromagnetic radiation) to heat a material? [closed]

While reading about microwaves, it occurred to me that I have no idea how energy from electromagnetic waves gets turned into heat. And how is the heating through microwaves different than the heating ...

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