All Questions
5,195 questions
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Photons are massless then how do they exist? [duplicate]
If something exists, then it surely has some mass. If photons are massless then they simply should not exist. But they not only exist but have momentum(p) also despite the fact that p=mv and if m=0 ...
- 213k
2
votes
2
answers
781
views
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 ...
CommunityBot
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3
votes
1
answer
379
views
Could sonoluminescence be the result of the Casimir Effect?
My question concerns Sonoluminescence. I was amazed to learn that collapsing cavitations in liquids generate temperatures greater than 20,000 Kelvin. Is it possible that the vast amount of energy ...
CommunityBot
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3
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6
answers
1k
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How is light as electromagnetic waves produced?
One of the upvoted answers to Why don't electromagnetic waves require a medium? says that the electromagnetic field is the medium for electromagnetic waves. It went on to say that if the ...
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4
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1
answer
2k
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Very large absorption lines in stellar spectrum
I was puzzled by the wide absorption lines in a stellar spectrum I found. The following is what I expect absorption lines to look like - thin, crisp lines:
However, I found this stellar spectrum, ...
1
vote
0
answers
61
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Can light exist in 4 spatial dimensions? [duplicate]
Light is electromagnetic radiation, according to what I have learned so far essentially a changing magnetic field inducing an electric field which induces a magnetic field and so on.
The equations for ...
- 213k
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1
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195
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A basic book (undergraduate level similar to Halliday and Resnick) about light scattering
In wikipedia:
https://en.wikipedia.org/wiki/Scattering
We read: Originally, the term (Scattering) was confined to light scattering (going back at least as far as Isaac Newton in the 17th century.
I ...
CommunityBot
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1
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1
answer
64
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1 watt of power defines as? [closed]
Imagine you have a light bulb of 1 watt power. Then, is 1 watt defined as
•1 joule of electric energy transformed to 1 joule of light energy in 1 sec?
•what exactly is meant by 'consumption' of energy ...
CommunityBot
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0
answers
51
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Color Isolation from Spectrum without Medium [closed]
Would it be significant if a specific color could be isolated from the spectrum without the use of a prism or filter? I wanted to see if I could do this as my current understanding is that it can’t be ...
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1
vote
1
answer
52
views
What causes shadows to be more saturated than the local color of the object?
I am a 2D artist who has recently been studying light and ray tracing to produce more realistic results. I have a general understanding of light now: specular, diffuse, bounce light, diffracted light, ...
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1
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1
answer
213
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How do plants absorb different "rates" of light?
Context
I'm trying to understand the broader question of why plants are green despite our Sun's "green" star status. This Wired article has a nice explanation, but I don't understand the key ...
CommunityBot
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25
votes
4
answers
8k
views
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 ...
CommunityBot
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1
vote
1
answer
2k
views
Sun light collimation
Is it possible to make sun light collimated in such a way, to increase energy density and keep it more less parallel?
like on the Earth we have intensity of sun approximately 1300 watt/m2. If we use ...
CommunityBot
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5
votes
5
answers
3k
views
How was the Ancient Greek theory of vision disproved?
Ancient Greeks and ancient Indians believed that the way in which vision works is that a beam goes out of the eye and hits an object. Whereas now we know that light reflects off the objects and then ...
0
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1
answer
184
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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 ...
CommunityBot
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0
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0
answers
26
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Methods to measure the IR intensity light using the Spectrometer
I'm a undergraduate student. Our group of friends plan to measure the IR light source intensity. We have a idea to do this.
In a dark room we place a IR light source in opposite to that we place a ...
12
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2
answers
1k
views
Is it possible to make a light follow a non-geodesic path?
I just stumbled upon this question.
For massive particles like an electron, it is easy to make them follow a non-geodesic path by applying an external force. In case of the electron, one can put it ...
- 10.8k
2
votes
1
answer
439
views
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 ...
- 458
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1
answer
245
views
How does silver affect transmission of energy in the visible and infrared part of the spectrum?
A common method to prevent radio frequency and microwave energy from going through windows is to apply a microscopic layer of silver to the surface of the glass, either by attaching a film coated with ...
CommunityBot
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0
votes
2
answers
84
views
Light bends in what path? [closed]
I have heard light bends around black holes because they are very massive. That is because the shortest distance there is the displacement along a non planar curved surface where Euclidean Geometry ...
- 2,446
1
vote
1
answer
109
views
Did I see the green flash, twice?
I was at the beach today at Costa Ballena in Spain. I was hunkered down to take a photo of the waves and the setting sun. Just as the last part of the sun was about to go below the horizon, I thought ...
- 2,007
2
votes
1
answer
45
views
Light radiation intensity equation [closed]
Is there an equation to convert Light radiation intensity from W/m² to Lux?
Note: The light source is the sun throughout the day (its intensity will vary over the day).
- 351
6
votes
3
answers
3k
views
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
1
vote
1
answer
487
views
How do you calculate light attenuation by wavelength at a given air mass coefficient?
I am trying to get a good view of light wavelength distribution as a function of viewing angle, with a specific interest as $z \approx 90^\circ$ near the horizon (sunrise/sunset). Air mass ...
CommunityBot
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2
votes
1
answer
79
views
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
4
votes
3
answers
2k
views
What actually causes light to diffract when encountering a slit?
I've researched this and there seems to be allot of information on how light diffracts, but very little on why. The light, when closely encountering the matter in the slit is 'bent' or rather changes ...
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0
answers
41
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Why is there a colour difference between stars and hot objects since they are both black-body radiators? [duplicate]
I have a question about the color of a black-body radiator that has been baffling me for a few years now, and I haven't been able to find a satisfactory answer. So, we know that a star's color depends ...
- 213k
1
vote
1
answer
37
views
How could I manually find the field of view of a camera lens at specific focal lengths?
I'm trying to manually find the fov of my FE 24-70mm F4 ZA OSS Sony full frame lens. I know I can find it on the internet, but I want to do a physics/mathematical investigation myself.
I have an idea ...
- 213k
6
votes
4
answers
1k
views
Why do telescopes converge light instead of diverge?
I am an astronomy hobbyist and have a 6" Newtonian at my home. While I was collimating my telescope it hit me that why is there a concave mirror at the back instead of a convex mirror.
Why do ...
- 10.2k
17
votes
4
answers
6k
views
What does the sky look like from the moon?
From pictures taken on the moon, it appears that there are no stars visible in the sky, but I do not know if this is an effect due to cameras.
What is the actual appearance of the sky on the moon?
...
20
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2
answers
5k
views
Why does one get an illusion as moon following him?
When you run or ride bike at night if you observe the moon you feel like he moves along with you as the same speed you are going. Why?
0
votes
1
answer
522
views
Quasi-fermi levels in a solar cell?
I was wondering, if my fermi levels splits up due to n and p type doping into two fermi levels, one for the p type one for the n type, and now due to light radiation my fermi levels split up into 2 ...
CommunityBot
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votes
2
answers
78
views
Why aren't brightness and loudness represented as spectra? [closed]
I'm curious why brightness (light intensity) and loudness (sound intensity) aren't usually described using a spectrum, which typically shows frequency ranges. Are these quantities measured differently ...
- 10.4k
3
votes
1
answer
351
views
Would Jupiter seen from near the planet itself, looks like it does in pictures?
Jupiter picture processed by one of citizen scientists
The picture above is artificially processed by one of the citizen scientists working for NASA. It was composed from monochromatic pictures taken ...
- 137k
0
votes
2
answers
61
views
What is the direction of the magnetic field of light?
So apparently light is a type of electromagnetic radiation. This implies that it has a magnetic field, which must have a north pole and a south pole. However, we only ever see light propagate one way.
...
- 3,359
0
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0
answers
13
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How did the first CRT monitors with Beam Penetration create a full set of colors?
Was reading about early CRT methods and came across the idea of Beam penetration, which from what I can tell was the first method of using these devices to make color images: two layers of phosphors ...
- 215
2
votes
2
answers
944
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Why do small particles differentially scatter colors (i.e scatter more blue light than red in Rayleigh scattering) while larger particles don't?
In both small and large particles, light as an EM wave will accelerate charged particles such as electrons and induce a dipole forcing the electrons to oscillate at the same frequency of incident ...
CommunityBot
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5
votes
1
answer
614
views
How to make a green LED as visually bright as a 0 magnitude star?
I'm trying to estimate the distance and power I'd need for a green LED to appear visually roughy as bright as a relatively bright star - say a visual magnitude of zero. Here is what I have so far.
Be ...
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2
answers
94
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Why does from blue to red light (after crossing a prism) the heating effect on interaction material increase?
I was reading this paper for Near Infrared discovery The history of near infrared spectroscopic
analysis:
In his experiment Herschel projected a rainbow on to a bench by the aid of a prism then he ...
2
votes
1
answer
342
views
Equivalence principle and bending of a light ray
In some explanations of a phenomena of curved spacetime we have an example of a light ray emitted in a freely falling space ship perpendicular to the direction of a free fall. In this case, for an ...
2
votes
4
answers
578
views
Why do different materials reflect different light?
So, as far as I understand, white light contains photons of all energy levels. These hit a material, say iron. The photons that are below the energy level to move electrons just pass through. The ...
- 475
1
vote
3
answers
525
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What specific properties of laser light make it dangerous?
What makes a laser more dangerous than a high powered single color LED for example?
Is it the fact that it's coherent light, all the photons have the same wavelength, that it can be focused to a small ...
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5
votes
6
answers
14k
views
Can light be trapped theoretically?
My question is a little silly I know, but I'm curious to know if a particle of light can be theoretically trapped between two reflective screens.
For example once the particle of light has left it's ...
- 12.9k
1
vote
0
answers
30
views
Transmission holograms
I would like to realize a transmission hologram for a college project. One of the requirements is to measure something with your own project. So I was thinking about measuring the diffraction index of ...
- 3,313
1
vote
1
answer
60
views
How to identify if a transparent material is made of glass or plastic from an image alone?
Without using any spectroscopy instruments, how to identify if a transparent material is made of glass or plastic (taking the below image as example)?
Background: I've noticed that the optical ...
- 4,193
1
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1
answer
626
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Plasma Frequency of Indium Tin Oxide
What does determine the plasma frequency? The formula is:
$$\omega_p² = \frac{4 \pi N e²}{m}$$
and for frequencies above the plasma frequency the material is transparent. So for indium tin oxide (...
CommunityBot
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-1
votes
1
answer
149
views
Is the grass greener on the other side? [closed]
Is it? I suspect that with different angles and such (but ignoring the basic structure of grass; resulting in you seeing mostly brown earth if you look straight down on grass) this might perhaps be ...
- 60.5k
0
votes
1
answer
296
views
Can a light block/reduce another light if projected in exact opposite direction?
For my project, I want to block a light passing through clear window glass temporarily, without manual work and without a curtain etc, want to be able to see through the glass, unobstructed if ...
CommunityBot
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8
votes
8
answers
10k
views
What do photons look like?
We have many theories that advocate the particle nature of light. But have we ever observed photons physically?
If so: what do they look like? How big are they?
If not: why not? Is it because they ...
0
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2
answers
96
views
Why does the critical angle decrease as the frequency of the light wave increases?
In my optics class a problem involved calculating the critical angle for a violet ray vs. a red ray (for total internal reflection), but I'm still confused on how the problem was approached. Could ...
- 36.6k