All Questions
5,195 questions
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Why does a blackbody object emit light if it only absorbs light?
I have learned that a blackbody object only absorbs light and thus does not reflect any light. The blackbody object will, however, emit light, and none of this light is due to reflection. Where does ...
- 471
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1
answer
75
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Seeking Visualization Tools for Hypothetical Black Hole Concept
I have a idea I'd like to explore: If a black hole can bend light due to its immense gravitational attraction, could we imagine an 'inverted black hole'? In this hypothetical scenario, this object ...
17
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3
answers
5k
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Why is the visible light spectrum different to a hue wheel?
The following problem has bugged me for a while, ever since I noticed it. On the Visible Spectrum Wikipedia, the following is the visible spectrum:
Now, in Photoshop, or really any colour picker, the ...
2
votes
1
answer
135
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Why rainbow colors are as they are? [duplicate]
There are handful of questions related to rainbow formation here already, but after looking into them, I feel that I must ask yet another one.
I did a little research on the subject, and most of the ...
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1
answer
76
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A friend of mine seems to believe that E=mgc. He believes that gravity and light are the same. That gravity is just photons not moving. Silly I’m sure [closed]
I don’t know how to frame the question because I lack understanding of physics. But it doesn’t make sense to me when he says E=mc2 is wrong or incomplete and that his formula of E=mgc is the ...
- 23
1
vote
2
answers
921
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Does refraction depend on the colour of light?
Consider passing red and yellow lights separately through the same interfaces and with the same angles of incidence.
Light of which colour will be refracted more?
This question was given to me. All I ...
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6
votes
8
answers
547
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Why specifically is looking through a telescope at the sun more dangerous than the naked eye?
At first this seems like a stupid question: "Have you never used a magnifying glass on a sunny day?!"
But any lens will only ever make the focused image as intense as the target or weaker. ...
1
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2
answers
515
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If photons are massless, how are they reflected and blocked by something that has mass? Shouldn't they pass right through any object?
If photons are massless, how do they get reflected, blocked when something comes in its way? Shouldn't the particle just pass right through any object?
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5
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3
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1k
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Why does light interact with normal matter but not with other light?
Why does light interact with normal matter but not with other light?
Assumptions:
Light does not interact with other light at all.
Light does interact with other matter, i.e reflection/refraction.
0
votes
1
answer
61
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Why does the dust in the sky make the light shine more or in other words it is visible from far away?
Why does the dust in the sky make the light shine more or in other words it is visible from far away?
This image shows how light is scattered in dust particles]1
2
votes
2
answers
121
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Relativity on a massive bridge
Suppose there is a ridiculously large bridge, fixed at either end (light seconds long at least). The bridge is constantly under the influence of gravity. If the ends are severed simultaneously, the ...
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1
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0
answers
54
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What is reason behind the curve shape of Rainbow 🌈? [duplicate]
We see rainbow 🌈 during rain but what excites me more that why always rainbow 🌈 are formed curve?
2
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3
answers
456
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Does passing through a colored medium cause light to become that color or to lose that color? Why is the atmosphere different?
It's well known the effect of Rayleigh scattering on the color of the sun, and it's explained several times on this website. Here's one of them. The summary of these explanations is, that when light ...
- 411
1
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2
answers
51
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How would we perceive light arriving to us from a distance source?
Imagine being in space 5 light minutes from the source of a beam of light. The source of the beam of light is initially switched off.
The light is turned on. When it is turned on you would see ...
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1
answer
89
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Why do sun emit light of different frequencies? [duplicate]
The sun emits white light, which is a mixture of light from all frequencies. Instead, it should have emitted a beam of light of the same frequency, as the source is the same?
So, can you please ...
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1
answer
100
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Why $\rm ZnO$ looks transparent?
I'm looking for the reason transparent of $\rm ZnO$ and found out nanoparticles of $\rm ZnO$ do not scatter reflected light
can I conclude like this: material can be transparent if pass light or ...
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1
answer
83
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Is it possible for photons to gain mass and interact with the higgs field? [closed]
If objects gain mass as they approach the speed of light, is it possible that as a photon "attempts" to exceed the speed of light it gains enough mass to interact with the higgs field ...
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2
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285
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What are the hex color code equivalents for the different classifications of stars?
Stars appear to be of various colors based on the visible light they emit. I am wondering if there is a hex color code that can be considered to be typified or average for the various classifications ...
- 143
3
votes
2
answers
141
views
Is “imperfect black”, (anything other than a black hole or vacuum), actually a color?
Is “imperfect black”, (anything other than a black hole or vacuum), actually a color?
Nothing absorbs all light except for a black whole, or a vacuum which doesn’t reflect light. If we consider black ...
- 31
2
votes
3
answers
307
views
Single slit (double slit) experimient to show a photon acts a particle
I have read explanations and watched videos about the double slit experiment and the interference pattern and I believe I understand these.
However, I believe (correct me if I'm wrong) it is said, ...
- 183
1
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0
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23
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Can Raman scattering (vibrational energy) of a diatomic molecule be described using work instead of potential energy?
From the literature, a diatomic model is often used to describe vibrational energy due to the inelastic scattering of light: two bodies (to represent charges) connected by a massless spring (to ...
1
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1
answer
201
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Why do fluorescence microscopes use long-pass dichroics
Superresolution fluorescence microscopy is very sensitive to chromatic aberration. Dichroic mirrors, while being biplanar, are not normal to the optical axis and so will cause some dispersion in one ...
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25
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4
answers
8k
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Why can't sunlight reach the very deep parts of an ocean?
Sunlight reaches the surface of the ocean and refracts. So it is still there. And its speed is about $225000$ km/s in water which is still incredibly fast. Light is a massless electromagnetic wave. So ...
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0
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39
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Limitations of Spectral Sensitivity Of Color Negative Film
I am trying to gain some understanding of film curves provided by the manufacturers of the film and I am confused about the Spectral Sensitivity curves. Take this for example (Screenshot of Kodak's ...
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1
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2
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272
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Snell's law and what determines color of light
White light is dispersed by a prism into the colors of the visible spectrum with wavelengths ranging from violet 380 to red 750 nanometers. By Snell’s law, the refractive index $n_{21}=n_2/n_1=sinθ_1/...
- 209
1
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2
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153
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Why didn't I reach $\frac{1}{p}+\frac{1}{q}=\frac{1}{f}$?
In optics for convex and concave mirrors there is the following formula: $$\frac{1}{p}+\frac{1}{q}=\frac{1}{f}$$ where $p$ is the distance between the object and the mirror, $q$ is the distance ...
- 422
2
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0
answers
43
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Why would this light beam look different from different directions?
I noticed a weird phenomena while in a particulate-filled restaurant with a sunbeam through a window. While facing the sun, the light beam was quite visible, but as you rotated towards facing away ...
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5
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3
answers
204
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Hyper-saturated blue colour in underwater explosions?
I've been looking at underwater explosions from various US navy shock trials:
e.g. https://www.youtube.com/watch?v=yV0eyP4nO20
and https://www.youtube.com/watch?v=PS2whGDzmzg
If you go frame by frame ...
- 117
2
votes
2
answers
308
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How can we visualize electromagnetic radiation?
In so many classes I’ve been told that light is nothing more than an electromagnetic wave. While this makes sense, it’s never been nearly as clear as imagining a static charge. At every point in space ...
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2
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360
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Is it possible for microwave beam to pass through non-metalic materials?
Greetings fellow physicists. I have some questions about the ability of different electromagnetic waves to pass through materials that I hope you can clarify.
It seems that microwaves can go through ...
2
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1
answer
79
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Why does light always make a rainbow on the surface of a bubble?
When light is refracted through little drops of water the rainbow is formed behind the water molecules.
When light is refracted through a glass prism the rainbow is formed inside the prism.
Then why ...
- 422
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0
answers
104
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Why does the Moon - which is grey - appear white to us even at daytime?
The color of the Moon as viewed more closely, is grey. But when we see it in the sky it appears white to us. Why?
Although this question has some answers here: Why is the surface of the Moon white? (...
- 411
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1
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68
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A question about colour temperature
This picture from Wikipedia is a table of temperatures vs colour for incandescence, however the problem is that I’ve been told that for a black body, even something with a temperature of say 2000C (E....
- 3,001
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2
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125
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On the level of Newton's particle theory of light
Huygens and Maxwell have wave theories about light.
On the other hand Planck and Einstein have theories about particle nature of light and could explain blackbody radiation and photoelectric effect ...
- 1,419
1
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2
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152
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How can photons be emitted from a star, travel millions/billions of years in a "straight line", and be seen by two adjacent observers?
If photons are emitted by a star and travel millions/billions of years in a "straight" line, they can be seen by adjacent observers. This makes it seem like there must be an uncountable ...
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1
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2k
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Calculating measured intensity of a Gaussian beam
Consider a light source which emits a Gaussian beam with total power $P_0$, initial width $d$, and divergence half-angle $\theta$ (in radians). The beam radius, measured from the waist of the beam, ...
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2
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0
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83
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Why are circular polarized 3D glasses for cinemas so cheap and working for a range of wavelengths?
Does anyone know how the filters in circular polarized 3D glasses for cinemas work (meaning how the filter on a micro-scale works, which material they use...)? Because in the lab we use of course ...
- 1,813
4
votes
2
answers
298
views
Unexpected rainbow in window
Lately, I observed a rainbow-like ring forming in my window during nighttime when the light enters from a street lamp. Interestingly, the sequence of colors in the rainbow seems to be reversed from ...
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1
answer
97
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Why does bright objects make less bright objects invisible?
I was walking by the sidewalk during the night when I noticed a swarm of flies circling a street lamp. It was difficult to see at first, so I tried looking in different angles. The security gate came ...
- 12.6k
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1
answer
107
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Rayleigh law contradicting tyndall effect
Sir, we have been taught that according to Rayleigh, the amount of scattering of light is inversely proportional to the fourth power of its wavelength and this law only occurs when the size of a ...
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1
answer
23
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How does the opening angle of a light source change the light field at a certain distance
I want to simulate the Intensity distribution of a light source on a plane some distance "d" away from the light source. If I assume the light source to homogenously emit light in all ...
0
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1
answer
39
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Propagation of two non-parallel waves
When a transverse wave is described by the equation, $y=A\sin(kx-\omega t)$,it is immediately meant that the direction of propagation is the $x$ axis with $y$ axis as the displacement. And we know ...
- 1,197
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59
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Direction of propagation not being parallel of two light rays
Here we can see two scenarios where in the first one are two Ray's whose ditection of propagation are parallel and hence we can say that they are in phase which means they interfere constructively.
...
- 1,197
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0
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Protocol to measure light transmittance of glass (for visible wavelengths)?
Which are common protocols to measure the light transmittance of glass (example: a window)?
I have searched for references and officials standards without success.
Which tools can be used to achieve ...
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votes
3
answers
840
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"Artificially" time dilated photons
If you bang on the table you create a single thump, but if you keep doing so with shorter and shorter intervals, eventually it'll start to sound like a note with a particular pitch.
Now, if I used a ...
- 313
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1
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290
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Was doppler effect for light proven experimentally?
If so, provide me with the data sources. From what I read, doppler for light is taken for granted. Or sometimes based on theoretical formulas. But if one wants to theorise, light is a mix of photons ...
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1
vote
3
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229
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What is the reason two rays originally polarized orthogonally but were rotated to parallel polarization does not visibly interfere even slightly?
The Fresnel–Arago laws by Augustin-Jean Fresnel and François Arago summarise some of the more important properties of interference between light of different states of polarization.
The laws are as ...
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1
answer
55
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Does the angle of refraction depend on an observer?
According to Fermat's principle, light should take the least time between two points. Therefore, is it correct to say that the angle of refraction is solely dependent on the difference between speed ...
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2
answers
110
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Does intense, cyclically-pulsed light appear brighter than its average?
Background
The Wikipedia article on the Talbot-Plateau law mentions:
If a light flickers so rapidly that it appears as continuous, then its perceived brightness will be determined by the relative ...
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3
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384
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Why doesn't the Intensity of laser light drop by $\frac{1}{r^{2}}$?
If we observe a laser we see its intensity wont drop by $\frac{1}{r^{2}}$ as seen for regular light sources as its very concentrated and even remain somewhat same for long distances (even though its ...
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