All Questions
5,195 questions
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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 ...
6
votes
4
answers
2k
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Does glass convert light wavelength?
I heard that when sunlight enters house through windows, it gets converted into longer wavelengths and gets trapped inside.
So does the glass have anything to do with this or is this about heated ...
- 539
1
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3
answers
190
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What is a laser spectrum?
What is a laser spectrum? How many wavelengths can we see in it, and why?
For a regular laser, the red ones you can buy at the store, is there just one red wavelength in the laser? Or are there ...
8
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5
answers
2k
views
Does color temperature limit how much a laser of a given wavelength can heat a target?
The Sun has a peak wavelength of around 500 nm and an effective surface temperature of 5770 K, and sunlight cannot be focused to make something hotter than the Sun, because this would be heat flowing ...
- 151
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7
answers
3k
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How does light beyond the visible spectrum relate to color theory?
Like if you put a red spotlight and a blue spotlight on the same area, the light ends up magenta. And if your light is purple and you have a yellow chair, the chair will appear black because the ...
- 26.6k
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0
answers
21
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Spectral bands of liquids and solids
I understand that instead of spectral lines, for solids and liquids spectral bands form, but why exactly do these bands form? I cannot see a reason why energy should be continuous now if photon ...
0
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6
answers
4k
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Why does light not produce sound?
We have heard about the definition of a wave - disturbance in the matter or something. But can we think that light is a wave and so does it have vibrations (oscillations). Does it produce sound then? ...
- 26.6k
0
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0
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27
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Solarization Spectrum
I'm looking to better understand the relation between the spectrum of the light which induces solarization in glass and the spectrum of the induced absorption.
More specifically, I'm interested in ...
- 1,558
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0
answers
79
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Is there a reason why in the astronomic pictures of galaxies and nebulosas there is so little green color?
From a quantum physics standpoint, why do astronomical images of galaxies and nebulae exhibit so little green color in their spectral composition?
When we look at the pictures of galaxies provided by ...
- 345
0
votes
1
answer
68
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Directionality of laser light in vacuum [duplicate]
It is well-known that laser light is directional because of coherence from stimulated emission. This means that the light is emitted ONLY in the direction of propagation, and not in any type of ...
- 5,207
7
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4
answers
5k
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What's at the end of a rainbow?
I recently saw a video where someone saw the end of a rainbow as it went into a lake. How is this even possible considering the fact that rainbows have no ends and are circular in nature?
Edit: I ...
-1
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2
answers
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 ...
CommunityBot
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votes
1
answer
344
views
Paradox of light passing through prism and glass slab
When white light passes through a glass slab, Newton's assumption is that a slab is made of 2 glass prisms placed in opposite direction, such that dispersion of both is cancelled out and a white light ...
CommunityBot
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2
answers
3k
views
Why don't we use a plane mirror instead of projection screen?
We know that a plane mirror can reflect rays more precisely so we can get a more accurate image. So why can't we use a plane mirror instead of a projection screen?
0
votes
1
answer
36
views
Exit Pupil, Objective Aperture, Magnification, and Brightness
Why is it that for two pairs of binoculars, with equal aperture, the one with smaller magnification has larger exit pupil and results in brighter images? If I understand correctly, the aperture ...
- 99.9k
-1
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2
answers
3k
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Is there anything that can produce light without UV rays?
I've read that everything from fire to LEDs can produce UV radiation. Generally, unless intended otherwise, lightbulbs will have a phosphor coating to prevent UV radiation from escaping the bulb. ...
- 1
1
vote
1
answer
345
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Diffraction limit of light
What is the diffraction limit of light? I see the following explanation in many papers on plasmonics:
Light can be focused to dimensions no smaller than roughly half the wavelength
What is the ...
CommunityBot
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10
votes
6
answers
1k
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Quantum interpretation of light coherence
When I studied interferences, I saw that only coherent sources could interfere.
In physics, two wave sources are perfectly coherent if they have a constant phase difference and the same frequency, ...
- 49
2
votes
2
answers
112
views
Why do gaps in my blinds create multiple lines?
Multiple lines appear on my floor every morning from the gaps in my blinds.
Why does this happen and does it have to do with light being a wave, like in the double slit experiment? If so could it be ...
- 213k
2
votes
0
answers
59
views
Do we perceive colors through energy or photon counts?
For example, assume a light color red such that its frequency is half that of another light blue.
If you were to have 1000 red photons incident on your eyes and 1000 blue photons, then the blue light ...
- 213k
0
votes
0
answers
29
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Can the rainbow illustrate the colors we can’t see? [duplicate]
Seen as how we’re only able to see a relatively small portion of the electromagnetic spectrum, does the rainbow “keep going” in the frequencies we cannot see?
In other words; if we were able to see ...
2
votes
2
answers
171
views
Why can't we see green color in the sky? [duplicate]
From sunrise to sunset we can see a variety of colors in the sky.
For example, during morning the most dominant color is blue whereas during sunset orange,red,yellow and there shades are more dominant....
- 9,304
1
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0
answers
55
views
What is the range of noon sun color temperature, when a light meter reports full expected sunlight (+/- epsilon)?
My question came from trying to find what uncertainty bounds, if any, I can assign to a color temperature sensor, without access to an artifact with a precisely calibrated output spectrum.
This leads ...
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3
answers
3k
views
Is it possible to get an electromagnetic wave equation if the speed of light were infinite?
In an old question: How would night sky look like if the speed of light was infinite? the best answer was voted down to negative credits.
I cannot understand why. From Maxwell's equations, we derive ...
- 324
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votes
1
answer
124
views
Lambertian surface and the luminous intensity
I am currently studying the basics of photometry to better understand the rendering equation of Kajiya. One thing I'm currently struggling with is Lambert's cosine law.
Let's go over the premises:
A ...
-4
votes
1
answer
89
views
Why does a ventilator appear to run leftwise and rightwise and back when spinning up?
My university professor, a friend of mine, asked me: "Do you know why, when a ventilator starts and during the process up to final speed, it runs clockwise and anticlockwise and back again to ...
- 51.7k
2
votes
2
answers
213
views
Understanding the Interference of Light
I would like to understand interference using 2 illustrations:
1) Bulbs send out light in all directions, right? If so, at a particular instant of time, shouldn't all the light waves coming out from ...
CommunityBot
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9
votes
2
answers
3k
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Why doesn't photon lose energy over distance?
In an atom, ( or even an oscillating circuit) When an electron falls from higher energy level to a lower one, it gives a photon of energy $hf$. On other hand it can be considered as an accelerated-...
4
votes
1
answer
110
views
Absorption respose of cones in eye
I am trying to find information about the absorption response of the cones in the eye to different wavelengths of light. I have noticed two types of graphs and answers: one which shows the S-...
- 213k
16
votes
9
answers
27k
views
Why can't we see infrared light?
While explaining to my nephew about the physics of light, I told him we cannot see infrared color, and he kicked back with a very simple question: why can't we see it? I could not tell him. Is the ...
- 916
20
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6
answers
4k
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Are human eyes the best possible camera?
I am not a physiologist, but whatever little I know about human eyes always makes me wonder by its details of optical subtleties. A question always comes to mind. Are human eyes the best possible ...
- 150
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vote
1
answer
93
views
What is light? how is it connected to electromagnetic radiation?
I am trying to understand how light works and electromagnetic radiation, from what I understand charges cause disturbances in electric fields, which triggers a magnetic field, and then the back and ...
- 213k
1
vote
1
answer
243
views
Structured light, infinite focus
Im interested in projecting a static image across a room that stays focused over a wide range of distances from the projector, without re-adjustment, for a structured light setup.
ie, the target may ...
CommunityBot
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2
votes
1
answer
87
views
How do we see the wave of light if we are not at the end of it? [duplicate]
Given that light is an electromagnetic wave why is it that I can see the ray of light without my eyes being in the path of the ray? For example in this image:
The camera is at the side and looking at ...
- 363k
1
vote
2
answers
85
views
Light traveling long distances
I am a high school student and I always wonder if light is an EM wave, then how it can travel such large distances? I tried to search on the internet but the answers have solution of Maxwell's ...
- 15
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votes
1
answer
98
views
Doubt regarding time lag during photoelectric effect
Recently,I was reading about the photoelectric effect and have a doubt regarding it:
Suppose I irradiate a metal surface with a monochromatic beam of light of frequency 'μ' such that μ > μ0 where ...
- 517
4
votes
1
answer
907
views
How can light be stretched (redshifted) if the speed of light is constant?
If light travels at the same speed how can it be stretched to provide red shift that is used in measuring the expansion of the universe?
3
votes
1
answer
3k
views
Different colors and their heat absorption capabilities
I did an experiment in which small canisters (image attached) containing water, were wrapped around with colour papers of different colours were kept under the Sun (image attached)
.
The different ...
- 2,210
5
votes
4
answers
1k
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Since computer screens can't display many colors, where can I go to see the full color gamut?
I found out recently that computer screens are only able to display a subset of all the colors visible to the human eye. Naturally one of my first questions was what do the other colors look like, but ...
- 1,276
1
vote
1
answer
58
views
Is it possible to see thermal columns?
The most common way gliders gain altitude is to circle in a thermal. Thermals are often found below cumulus clouds, or above dark areas on the ground. Without these signs, they are harder to find and ...
- 363k
0
votes
1
answer
34
views
Color changes with polarization
Plane polarized light is passed through a second polarizer whose polarizing direction is, say, at $80^o$ to the polarizing direction of the first polarizer. How does one experimentally measure the ...
- 45.7k
13
votes
5
answers
7k
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How do photons have temperature?
On the internet, I found
"Temperature is a measure of the average kinetic energy of the particles in an object."
(source)
So, this temperature should be a result of friction.
Light is also ...
- 434
0
votes
1
answer
104
views
Does a mirror have an albedo of 0?
According to the Wikipedia definition of albedo, it measures the fraction of light that is diffusely reflected by a body.
Let's consider the visible light wavelenghts; is a mirror an object with an ...
- 28k
5
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1
answer
1k
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What mistake did Einstein make in 1911 when he miscalculated the light deviation?
When Einstein published the general relativity theory in 1911, why was the light deviation not predicted correctly? What was the incompleteness of the theory when he published it in 1911? When and how ...
- 155
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2
answers
60
views
What exactly happens to a light ray that is incident on the vertex of 2 mirrors inclined at some angle
So the question I had was that if we have two mirrors as shown in the diagram, what exactly occurs to the light ray that is incident on the vertex of the mirror? If we would like to construct the ...
- 20.4k
1
vote
1
answer
58
views
Would we be able to see the superposition of two X-rays where the frequency of the modulation matches visible light?
Suppose I had the superposition of two electromagnetic waves whose angular frequency was in the X-ray region. Together they form a composite made of a carrier wave and a modulation wave where the ...
- 531
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votes
2
answers
549
views
Is there an equation that can estimate chances of alien life in the universe?
Seeing how infinite the universe appears and out of all of those stars, planets, galaxies, there must be other life forms. Mathematically, the odds are very good. Is there a mathematical equation to ...
CommunityBot
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0
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46
views
How to determine if an observer can see an object with multiple mirrors?
How do I determine if an observer can see an object with multiple mirrors? I came across this image online and I am wondering if the observer (point O) see the object (point A)
My attempt:
I tried ...
- 12.9k
2
votes
4
answers
429
views
Why electrons do not emit electromagnetic radiation when they "jump" to an excited state?
According to electromagnetism, accelerating charges emit electromagnetic (EM) radiation. However, according to quantum mechanics, electrons do not emit EM radiation while they "orbit" around ...
- 41.4k
9
votes
3
answers
35k
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How does the anti-gravity fountain work?
I just saw this video of an anti-gravity fountain on youtube, but I can't understand how you can reverse the flow of water.
I know you can stop the flow of water by using something called a ...
- 2,165