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.
4,997
questions
5
votes
3
answers
222
views
Connection between photons and EM waves
We learn about electric and magnetic fields and how they conform EM waves. Then we discover the photon and how there was a duality between this two ideas, sometimes radiation behaved like a wave and ...
- 51
1
vote
0
answers
46
views
Are there any nonlinear crystals or other transparent materials that can produce anti-Stokes, phase matched, frequency shift of laser light?
While some nonlinear crystals can convert incoming laser light into harmonics, thus for example doubling the light frequency, are there any crystals or other transparent materials that can reduce the ...
- 204
0
votes
0
answers
48
views
Schlick's approximation for reflectance when $n_1 = n_2$
another raytracer here.
I'm using Schlick's approximation to the Fresnel equations, which is said to be reasonably faithful.
I'm a little puzzled about the situation where the incident ray is just ...
- 101
6
votes
3
answers
2k
views
What property of light allows it to propagate in space? [closed]
I got this question in a university entrance exam; I'm not sure what could've been the answer. I've scoured the web and could hardly find a decent answer. The question and choices were:
What property ...
8
votes
1
answer
495
views
Skylight reflection shows birefringence patterns
I noticed that the skylight where I work looked white to me, but its reflection from the tiles below showed a colorful pattern. See the images below, and also a video that shows this effect from ...
- 11.9k
2
votes
1
answer
60
views
Confusion about EM absorption [duplicate]
I have now encountered various explanations on how matter interacts with electromagnetic waves (EM) but it still seems like an unconnected mess. The best way I can demonstrate my questions is with an ...
- 167
1
vote
0
answers
37
views
Why are the hottest stars appear mostly in blue or blue-white? [duplicate]
Does it have to do with anything regarding wavelengths and frequencies..
- 11
0
votes
1
answer
44
views
Phase change in a wave travelling through different media
Suppose I have a wave, and two mediums with different indices of refraction. When the waves pass through these two mediums, will there be a phase change between the waves that comes out from the first ...
1
vote
3
answers
286
views
How does light not have mass? [duplicate]
How is it possible for light to have zero mass because it was my understanding that in order for "stuff" to exist it has to have some form of mass? And if it does not have mass then can it ...
-1
votes
1
answer
52
views
Can an atom according to Bohr's model be considered a black body?
I recently read about Bohr's atomic model and found out that an atom tends to absorb all the energy of a particular frequency to excite its electron and it also gives the same amount of energy that it ...
3
votes
0
answers
58
views
Why is sunset in mars blue?
This is the Martian sunset, as captured by the Spirit rover of NASA. Notice the colors are inverted, i.e. the direct rays blue and diffused rays red, which is exactly the opposite of what you would ...
- 11.9k
-2
votes
1
answer
82
views
Why does sound travel in a wave? [closed]
Sound waves carry energy. Why does sound travel in a wave instead of a straight line when travelling in a wave covers more distance and is less energy-efficient than travelling in a straight line? ...
0
votes
0
answers
32
views
Is there really a relation between light intensity and color saturation?
Going through this article on Wikipedia, under the saturation section, I came across "The purest (most saturated) color is achieved by using just one wavelength at a high intensity, such as in ...
- 1,096
0
votes
1
answer
72
views
How to explain interference pattern in our eye?
Suppose we got a Lamp L that emits some light. The light afterwards hits a diffraction Grating G at a distance a. Now if you were to look through the grating with your Eye E, you were to see the ...
- 452
2
votes
0
answers
39
views
What will happen to the light due to frame-dragging?
Imagine a rotating black hole is blocking a cluster of stars that I'm observing. Thanks to gravitational lensing I could still see the stars albeit shifted away from their original locations. So now ...
- 13k
0
votes
0
answers
17
views
Does anyone know the correct way to verify the color temperature of a given light source in a color booth and the equipment needed?
ie. spectroradiometer on the floor (constant distance) of the booth directly measuring the "observed" color temp emitted directly from the light source? is it more acurate to measure the ...
- 1
-2
votes
2
answers
80
views
Amateur Shower Thought Question About Time and Space
Apologize in advance if this is the wrong group. I often watch Netflix shows about blackholes explained in a nutshell or laymen’s terms.
I had a recent thought/scenario that may relate to some ...
- 99
0
votes
1
answer
68
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 ...
6
votes
2
answers
2k
views
Wavelength of "complementary colours"?
In physics/chemistry/the life sciences there's a common experimental method of determining the concentration of a sample using spectrophotometers. We can measure the absorbance of the sample at a ...
- 596
1
vote
2
answers
175
views
Do the interference of two EM waves with the same frequency but different phase cause the EM waves to slow down?
So this question is inspired by the explanation of EM waves slowing down in a material through interference with waves produced by the material in response to the incoming EM wave. You can see ...
- 319
1
vote
2
answers
52
views
Conflicting lensmaker's equation representation
I keep finding these two conflicting forms of the lensmaker's equation. I understand that (n2-n1)/n1 is the same as (n-1) if referring to a lens in air, but I can not make sense of why the reciprical ...
- 23
0
votes
1
answer
38
views
What happens to a photon leaving a grav well if it doesn't have the energy to get out of the well and the object it's leaving isn't a black hole?
Light exists with energy E = hf. That is supposed to be quantized and discrete but maybe "f" in the equation is continuous when not emitted specifically from an electron (moving through the ...
- 1
2
votes
1
answer
105
views
Does the probability wave of a photon determine its color?
The wavelength or frequency of light determines its color. Photons seen as particles are said to have a frequency, determined by its energy, so I assume that 'is' the same color.
But being quantum ...
- 579
3
votes
1
answer
54
views
Can a system of lenses or compound lens have a higher numerical aperture than a single element in the system?
I am attempting to create a simple Abbe condenser for a microscope, which typically consists of two converging lenses.
Ideally, I would like to achieve a numerical aperture for the condenser of ...
- 33
1
vote
2
answers
41
views
Do there exist materials whose Opacity varies with temperature?
Do there exist materials whose Opacity varies with temperature?
E.g a Material that becomes more Opaque as it gets hotter?
- 2,870
0
votes
0
answers
54
views
Is the Fourier Transform a reliable way to infer the physical phenomena producing an RF signal?
Consider the following thought experiments:
Scenario 1:
A person standing far away shines 3 light beams at you, each beam having a narrow spectral distribution centered around different frequencies F1,...
- 139
0
votes
0
answers
25
views
Is it preferable to say $v$ is " image distance " than to say " image position " in spherical mirror formula?
I was going through spherical mirror formula $1/v + 1/u = 1/f$ where $u$, $v$ and $f$ are named as object distance, image distance and focal length respectively. But while using this equation we do ...
- 1,239
0
votes
1
answer
53
views
Can I recover the physical wavelengths present in a light source from a time-series measurement of its amplitude?
Consider a mixture of different wavelengths being emitted from the same point (ex: a star). This light consists of a mixture of wavelengths and intensities at each wavelength. When measuring the ...
- 139
3
votes
2
answers
920
views
Would the "FFT" of a light source be a reliable indicator of perceived color?
Paraphrasing from here:
A purely monochromatic 575nm wavelength light would be "perceived" as yellow, as would a light that has equal components in red and green (but no yellow). However, ...
- 139
1
vote
1
answer
88
views
450nm peak absorption [closed]
I am looking for an oxide compound (metal oxide, or similar preferably inorganic) which shows light peak absorption at 450 nm. I have troubles in finding the right compound, as most of the oxides have ...
- 113
24
votes
1
answer
7k
views
Based on my calculations, we cannot see the Earth from the ISS. Obviously it's wrong. Why?
What started as a fun exercise really annoys me because I cannot see where I got it wrong.
I initially wanted to see how many photons hit a pixel of a camera on the ISS pointed at the Earth - but I ...
- 987
0
votes
2
answers
46
views
Is reflected color not from the wavelength corresponding to that color?
I was reading through Josef Albers' interaction of color (a classical art color theory book), where he makes this point:
If I see a substance, or pigment of a particular color, doesn't that mean I'm ...
- 1,096
0
votes
0
answers
52
views
Derivation of optical resolution
I'm trying to prove optical resolution formula from scratch and im having a hard time doing it. I dont know much about optics (im studying cosmology) and i need a detailed proof of optical resolution ...
4
votes
5
answers
459
views
Is the speed of causality slower in water?
I've recently read that what most people learned to think of as the 'speed of light' is actually the 'speed of causality', and that light just happens to travel at that speed (through free-space.) I'...
- 453
4
votes
1
answer
156
views
Number of fog droplets in the air
I have an issue with the official solution to this problem from BelPhO:
Visibility on the road is 100 m. Assuming that the diameter of a fog
droplet is 1 micron, estimate the concentration of fog ...
- 423
6
votes
2
answers
542
views
How smooth must a surface be to produce specular reflection, and do Lunar boot prints meet this standard?
Question: How smooth must a surface be to produce specular reflection, and do Lunar boot prints meet this standard?
A recent post on Space Exploration asked why footprints on the moon displayed ...
- 189
0
votes
2
answers
74
views
Does Law of Reflection gets violated?
I was curious as to why the "Law of Reflection" is only a law and not a principle. Are there any specific conditions or circumstances where it is not followed by chance? If so, how so?
Note: ...
- 54
1
vote
1
answer
132
views
Why are diffuse white highlights on matte objects as bright as they are?
The reason we can see the color of objects is light rays undergo scattering in the subsurface of a material, and in their walk in the material lose some wavelengths, and finally exit at a random ...
- 1,096
1
vote
0
answers
45
views
What is the connection between Ray (Geometric) optics and Electromagnetic theory optics in fiber optics?
I am currently reading about fiber optics and wave propagation in fiber optics and encountered the following part of Gerd Keiser's Book :
according to the diagram shown, its a general case when the ...
1
vote
0
answers
66
views
Does our sense of color depend on frequency of source or the wavelength of light?
I was taught that the colors we see are results of the corresponding wavelength, but each wavelength also has a distinct frequency since speed of light is fixed for a specific medium (same goes for ...
- 169
8
votes
5
answers
2k
views
Do colours which are not visible to human eyes exist?
Are there any colours that our human eye cannot comprehend but other animals can see? The ability to see colours is the property of our eyes. For example an average dog would see less colours than us. ...
- 412
0
votes
1
answer
77
views
Does two same light bulbs produce light of same frequency? [duplicate]
If they do, then why don't we observe interference in normal rooms? And if they don't have the same frequency then why is that so?
0
votes
1
answer
42
views
Why do photons change direction when they pass through a optically denser/rarer object?
For example, during refraction, when photons pass through a glass slab, they change direction. Why does this happen? Is the reason for this not applicable when photons strike perpendicular to the ...
0
votes
0
answers
15
views
What effect, if any, does dissipative absorption have on aurora borealis? Why don't we see more colors as a result?
According to wikipedia, the aurora borealis is primarily caused by charged particles from the solar wind being redirected to the poles by earth's magnetic field and slamming into the nitrogen and ...
- 57
10
votes
2
answers
2k
views
Is it possible to witness a rainbow while facing the sun?
We know that a rainbow occurs due to the refraction and reflection of light inside raindrops. We also know that inside spherical raindrops total internal reflection is not possible. So some light is ...
- 123
-1
votes
1
answer
120
views
Relativistic momentum for light
In special relativity,momentum $p$ is defined by $\gamma mv$ where $\gamma=\frac{1}{\sqrt{1-\frac{v^2}{c^2}}}$. Again,we are aware of the relation $E^2=(mc^2)^2+(pc)^2$. Now,the momentum of light is ...
- 1,191
1
vote
0
answers
32
views
Why are no industrial diode lasers deep cooled?
Endurance lasers showed that a 633nm laser diode could lase as low as 621nm when cooled to almost -80C. The wavelength shift for diode lasers can surpass 0.3nm/‘C. From my limited experience ...
- 106
0
votes
2
answers
97
views
What is the colour of an atom? [closed]
We know that when an electron jumps from shell to shell it produces light waves which produce the sensation of vision to our eyes. But can anything be said about the colour of an atom in particular. ...
- 85
1
vote
3
answers
71
views
Wavelengths of light outside our solar system
The question might have been asked before. Our Sun's rays decompose into 7 elementary colors by using a prism or spectrometry. Can the the colors (their number and wave length in the spectrum ) be ...
- 1,012
-1
votes
2
answers
245
views
A object viewed from a red glass would appear red colour? [closed]
Original Question:
Explain, why in daylight an object appears red when seen through a red glass and black when seen through a blue glass?
My understanding according to what is given in my textbook ...
- 105