# Tagged Questions

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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### Can we produce energy by red-shifting light

The answer on my question Does light accelerate as it nears a black hole? leads me to think that light 'gains' the gravitational energy by shifting to a frequency with a higher energy (blue). Is this ...
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### Color(Light) Absorption [duplicate]

As per my knowledge orange color object (say orange) absorbs other color light except orange color light. So we can see orange object as orange. If this is true then is it possible "In a ideal light ...
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### Does light accelerate as it nears a black hole? [duplicate]

As light is affected by gravity ( gravitational lending and black holes), it would seem that gravity causes acceleration. Acceleration has two parts: direction and magnitude. It is clearly evident ...
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### Can a high-watt laser's scattering light be damaging to the eyes? [closed]

Heyo, I recently purchased a S3 Arctic Class IV laser pointer. I bought the 3500mW. (In case that page expires, it's 445nm wavelength, 1.5mRad variant, NOHD is 279m, beam distance at 0.25 Lux 72km.) ...
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### If a car is travelling faster than the speed of light, do the headlights still work? [closed]

If a car is travelling faster than the speed of light, do the headlights still work? If you can help because i really need to know i am going on a trip with my car tomorrow!
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### If light slows down while passing through a material, does it speed back up while in a vacuum?

Light slows down while passing through, say, water. After passing through the water, does the light speed back up to the "speed of light"? If so, how and why?
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### Can we look across Time? [closed]

A photon moves across space, but it does not move across time. If we look at a galaxy that is 1 billion light years away, then we see that galaxy as it appeared 1 billion years ago. Now the ...
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### Frequency or Wavenlenght; which changes when light is passing from rarer to denser medium? [duplicate]

what changes; Frequency or Wavelength when light passes from a rarer to a denser medium?And Why?
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### Scaling of the CIE RGB color matching functions

In the CIE color system, the RGB color matching functions look like this when plotted (I'm unsure what the unit of the Y axis is) https://en.wikipedia.org/wiki/CIE_1931_color_space#CIE_RGB_color_space ...
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### Laser shone at liquid jet

When a liquid jet of water falls in laminar flow, it hits a surface. If this contact point, between the surface and the jet, is illuminated by a laser. Rings of light can be seen forming around the ...
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### How exact does the wavelength of light have to be to be absorbed by an atom? [duplicate]

I have been reading sources such as this on absorption and emission which make statements such as: The interesting thing is that each atom will only absorb photons with exactly the right energy. ...
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### When is an image formed?

Every part of the page is illuminated with reflected light from your forehead, your nose, your chin, and every other part of your face. You don't see an image of your face on the page because there ...
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### does colour of compound affects the specific optical rotation at defined costant temperature and wavelength?

If analyte has a defined method of analysis for the Specific optical rotation. is it possible a change in specific optical rotation due to change in colour of same substance?
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### Can light be warped by a magnetic field? [duplicate]

I was thinking and came up with the question "Can the path of a photon be warped by a strong magnetic field?" I tried searching online for an answer but couldn't find much scientific evidence of it ...
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### Does every light ray have a normal?

I am currently learning about light rays and how we see things and I have recently learnt about the normal, an imaginary line. I was wondering if every light ray has a normal? Thanks.
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### What happens to light when an optical cavity path length doubles instantaneously?

Let's say we have light contained in a cavity (of initial length $L$) and then instantaneously remove the second mirror, thus removing the barrier between the first and a third mirror which is some ...
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### Light waves and water waves

I have an idea and i would like to have more information: If I drop a stone in the water some rings or waves will appear. Those rings are made of water and are behaving that particular way because of ...
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### Are the colors of the rainbow absolute or arbitrarily assigned? [closed]

I was watching a multi-colored loading icon, and it piqued my interest. Red, orange, yellow, green, blue, indigo, violet. (Is indigo a real color? I don't know, but that's what I was told growing up)...
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### Is it possible to save the light?

I am just thinking why can't we save the light (not a bulb). Lights normally get reflect by mirror, when source is off reflection is gone or absorbed or discharged by other object in room. Can't we ...
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### Light's speed constancy

Trying to understand the special relativity I faced a problem,and have a question, well, with the speed of light being constant in every frame, the operation s=d/t (s for the speed of light d: ...
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### Why can I see through a window but not a wall? [duplicate]

What is the difference between a window and a wall that makes a wall opaque but a window transparent, in terms of the molecules that make them up?
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### Light pollution and visibility of Milky way [closed]

Say, 1000 years ago, when there was (almost) no light pollution or air pollution, would the milky-way galaxy have been visible at night, anywhere on Earth?
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### Light field 5D Plenoptic Function

Wikipedia says "Since rays in space can be parameterized by three coordinates, x, y, and z and two angles $\theta$ and $\phi$, as shown at left, it is a five-dimensional function" I'm not ...
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### I would like to know if violet bends the least or red [closed]

I had read that violet bends the least. But most of the webpages state that red bends the least. I would like to know why it is so.
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### Blackhole and light [duplicate]

I was talking with my friend about blackholes and I asked him "Why blackhole 'sucks' the photons?" He had no deeper understanding so he answered that "I dont know, may the light is affected, because ...
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### Can light projection on a wall travel faster than the speed of light? [duplicate]

If I project a flashlight beam on a wall and turn the source, the projection (as seen on the wall) is seen moving along the direction of the turn with some speed. If I have projected it on a gigantic ...
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### Amplitude at successive wavefronts?

Consider spherical waves emanating from a point source initially the amplitude is A, as wave travels forming wavefronts will the amplitude of each point in all the secondary wavelets be the same and ...
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### physics of color in glints

Below, I show zooms on the glints on 3 materials: (clean) metal blade, stainless sink, artificial leather (but same effect shows on human skin). Only the sink was under artificial light. What I'm ...
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### Is it possible to split a photon? [duplicate]

I read that if two photons collide than theoretically it would make light convert to matter. If you split a photon into two, will it convert matter into light? I'm a huge amateur so excuse me if this ...
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### Light at the Speed of Light [duplicate]

Since light particles travel at the speed of light, we know it's possible for something to travel at that speed. However, since all things are relative, and if time does stop at the speed of light, ...
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### Does light have mass? [closed]

Does light have mass? If yes, will it exert force? If no, then how are light particles are travelling at light speed? If light doesn't have mass how is it attracted by gravitational force (black holes)...
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### Where does the energy lost due to light emission come from?

If an object lose energy when it emits light, does that energy come from the mass of the object? Examples: Does a flashlight lose mass when it's turned on? Does a regular object (like a pencil or a ...
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### Curious question about light and photons

If a photon wavelength (e.g., yellow) is isolated from the other wavelengths that the sun emits (once it gets to earth), can that particular particle/photon be distorted slightly into a wavelength ...
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### How come lenses alter the path of photons?

From what I know, photons are theorized particles and believed to be massless (just energy) and travel at the speed of light. How come a lens, which is an object made of atoms, can bend a light path? ...
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### Why is my shadow deformed and not the shadow of the ceiling? [duplicate]

Look at these two photos of my shadow from sunlight. Case 1: My shadow is separated from the shadow of the ceiling and my head is round. Case 2: But when I walk a little more and the shadow of my ...
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### How does gravity affect different bodies? [duplicate]

To my understanding,the force of gravity increases as the mass of the body increases (ex. the moon has less gravity than the earth). So, intuitively, I would come to assume that the force of gravity ...
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### Where do the energy and momentum come from when light is perfectly reflected on a surface?

If you send a light beam to a surface which reflects the light perfectly I would say that on the surface is put a force of the light so the surface moves backwards. But where does that energy comes ...
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