All Questions
5,195 questions
9
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3
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What is the best way to collimate light emitted by a LED? [closed]
I'm new to this forum. This is half a question, half a challenge. And it's more engineering then physics but I thought I might get good insights from a physics forum.
I would like to cure a UV ...
0
votes
2
answers
40
views
Creating pure monochromes by separating constituent waves
Since we cannot create a pure monochromatic wave, consider a white light wave and let it pass through a prism. Are the colored waves produced by this non-monochromatic as well? If yes, then can't we ...
- 20.4k
4
votes
3
answers
2k
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Why can you see a light in the location that the light source just left?
This is my first question on this site so forgive me for the awkward wording of the question. Basically, my question is why does light from, say, a sparkler, seem to remain where it just came from to ...
- 1
33
votes
3
answers
7k
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What do the stars really look like, if you could travel at almost lightspeed?
I heard that the way light speed is shown in the movie "Star Wars" is not realistic.
About 1 month ago in a documentary on TV they said that it would be the opposite of the way it looks in "Star Wars"...
1
vote
1
answer
74
views
Fresnel Equations and an Opaque Surface?
I'm trying to make sense of what actually happens to light when it interacts with an opaque surface.
The fresnel equations give us the proportion of light which is reflected off the surface of a ...
- 4,300
0
votes
3
answers
836
views
Could time dilation bend the path of a photon? Does time dilation have a refractive index?
The main question I am getting at is, does time dilation have a refractive index? What I mean is, if I were to shoot a laser past a black hole, would the laser's path "bend" strictly from time ...
-1
votes
1
answer
57
views
Why light have gravitational lensing? [closed]
I was reading about light in a book there it was there that light is not a physical quantity, light has no mass as photons are more and more smaller then atoms. Then how does gravity affect the path ...
- 4,193
0
votes
1
answer
88
views
Why does Sun appear white at noon?
I have found several source citing the reason for the white apperance of sun is due to less scattering of light before sunlight reaches an observer on the Earth (as it is relatively closer to us at ...
- 99.9k
21
votes
8
answers
6k
views
Why don't objects get brighter when I reflect their light back at them?
In a well-lit room, a light source shines light on the objects in the room, some of which reflects back off the objects. We can make the light source brighter by causing it to emit more photons, which ...
- 13.2k
12
votes
5
answers
6k
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What would the RGB color value of an infinitely hot blackbody be?
In other words, what is the limit of the rgb values of color temperature as temperature approaches infinity? Put differently, what is the terminal point of the Planckian locus? Is there an exact value?...
- 141
-5
votes
2
answers
88
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If light can't have relative speed, does it get left behind the earth imperceptibly? [closed]
I was just thinking about how if a planet is moving very quickly through space, everything we "throw" from it with mass would leave with a momentum from Earth, like a ball dropped in moving ...
- 530
1
vote
1
answer
904
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How is red colour from from rainbow hotter than blue (W. Hershel) if it has lower frequency than the latter?
We know that blue light has a smaller wavelength and higher frequency than red light, which is a consequence of higher energy in the former, then how is it true that, when scattering light from the ...
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4
votes
1
answer
220
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While flying over Rome we noticed that during sunset, there was a green color between the red and blue of the sunset sky. What causes it?
The picture has only been trimmed and not edited. The green is visible when the red or orange tapers off into the blue. Is this different from what causes the green flash? We were flying from Rome.
CommunityBot
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1
vote
1
answer
265
views
How can you show with a diagram that diffraction is at a maximum when the slit width is equal to the wavelength?
Usually a diagram will be given like this
But how can you show with a diagram that diffraction can be maximised when the slit width is of the order of the wave's wavelength?
CommunityBot
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36
votes
10
answers
35k
views
Is coherent light required for interference in Young's double slit experiment?
In this Veritasium video, a home experiment is presented which appears to produce a very good double-slit interference pattern with normal sunlight.
The experiment is an empty cardboard box with a ...
- 121
24
votes
4
answers
19k
views
Do eyeballs exhibit chromatic aberration?
Fairly straightforward question. If not, why not?
I suspect that if they do, it is not perceived due to the regions of highest dispersion being in one's region of lowest visual acuity.
- 52.4k
0
votes
4
answers
604
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Light Spectrum - Sum of Waves or Collection of Waves
I am wondering about the spectrum of light that is often shown pictorially as a distribution of power, say, from sunlight. My question is: does this indicate that each wave of light contains all of ...
CommunityBot
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6
votes
3
answers
31k
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UV reflective surfaces
Do surfaces that reflect visible light efficiently also reflect UV light? If not, are there surfaces that do?
(I have a large array of UV LEDs that I need to make larger and more diffuse, so I'm ...
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-1
votes
1
answer
76
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How was the speed of colored light measured in a vacuum? [closed]
Light is affected by the change in the speed of the source as the frequency of light changes. This is called the Doppler effect, where the red shift can be observed in galaxies moving away from us.
...
- 109k
2
votes
3
answers
611
views
What is the refraction index in the upper atmosphere (e.g. thermosphere)?
I've been searching for the refraction index in the upper layers of atmosphere such as stratosphere and thermosphere but I can't find it, all that I've seen is all equations without any numbers that I ...
CommunityBot
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-2
votes
2
answers
128
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Can Young's slit be repeated in the temporal dimension with fast-oscillating lcd's?
Can Young's slit be repeated in the temporal dimension with fast-oscillating lcd's?
Young's slit demonstrates the wave-like properties of light by causing interference from two slits. Fringes caused ...
- 841
3
votes
2
answers
467
views
If light is electromagnetic wave why magnetic compass work in presence of light?
I understand light transfer through space as an oscillating electromagnetic field just like sound wave travels through air making air molecules compress and expand.
Now as we already observe effects ...
- 69
3
votes
1
answer
243
views
How do LCDs vary light intensity?
What exactly happens when an electric field is applied?
Say we're dealing with a TN LCD, in a 'normally white' mode.
With no voltage applied, the orthogonal grated plates cause the director of the LC ...
CommunityBot
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0
votes
1
answer
211
views
Is thermal EMR just another form of Fluorescence / Phosphorescence?
Normally when thinking about Fluorescence one only deals with visible light, but is it fair to say that the thermal EMR (heat) that's generated from a light source is also a fluorescent effect? For ...
CommunityBot
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2
votes
6
answers
2k
views
If light is electromagnetic then can light produce electricity or attract metals?
what I mean to say is that if light is electromagnetic in nature then shouldn't it show electric or magnetic properties on matters? Like if light falls on a metal it should produce current due to ...
- 69
4
votes
1
answer
2k
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Why does Light change color through Glass slab?
I shone a green laser light(~532 nm) through a glass slab and what I saw inside was that the light beam was now red.
Imagine a regular refraction diagram but color the beam outside green and that on ...
CommunityBot
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0
votes
0
answers
30
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Eternal Acceleration [duplicate]
I'm a physics graduate, so I have a solid understanding of special but not much knowledge of general relativity. I tried a thought experiment the other day involving a spacecraft accelerating ...
- 363k
1
vote
2
answers
139
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Does the color of glass affect its index of refraction?
I've found found lots of stuff on how the color of light relates to the index of refraction while holding the refraction material constant, but I'm looking at the opposite problem: does the color of ...
- 2,938
1
vote
1
answer
34
views
Why am I getting higher sensor output when I have the tube I'm measuring filled with fluid?
I have a custom project to detect fluid color and turbidity (a reduction in light passing through) using an Arduino micro, a TCS3200 sensor, and an LED. The tube sits in a custom housing, and the LED ...
1
vote
3
answers
2k
views
Newtonian Bending of Light?
I ran across THIS Newtonian explanation for the bending of light. Does it have any merit?
- 213k
22
votes
9
answers
14k
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Does Newtonian mechanics predict the bending of the course of light by objects with mass?
$$F=G m_1 m_2/d^2$$
$$F=ma$$
$$a_g=Gm_{\rm other}/d^2$$
In Newtonian mechanics, the acceleration of object A toward object B is not dependent on the mass of object A but on the mass of object B and ...
- 213k
0
votes
1
answer
520
views
Color of sky from an airplane
My textbook says that the sky appears black to the passengers of an airplane flying at a high altitude. They further explain it by saying that this is because of the fact that the atmosphere of that ...
- 213k
0
votes
3
answers
126
views
Can we cancel out light in the same way we do sound using interference?
I understand sound waves interfere and, if organised strategically, can cancel each other out to produce what is basically silence. My question is: since waves of light can produce their own ...
- 2,053
2
votes
2
answers
2k
views
Rainbow Colors on a Water Droplet on a Screen
I accidentally fell a water droplet on my mobile phone's screen. But on observing closely I saw that the water droplets showed rainbow colors (the screen was mostly white). By rainbow colors I mean ...
- 12.9k
1
vote
3
answers
238
views
Can the colors of white light be separated through reflection alone?
Can the colors of white light be separated through reflection alone? My answer to this is no since if we want to separate the colors, we use prism and when light passes through a prism, the dispersion ...
- 10.2k
1
vote
1
answer
49
views
Thin Lens in different media
I have been given an equiconvex lens (of given focal length), placed on a plane mirror, with water between the lens and the mirror.
An object has been placed at a certain distance and I have been ...
- 5,027
0
votes
1
answer
47
views
Doppler Shift in Moving Medium
Would the medium between a stationary source and observer moving cause a shift if the source and observer are on opposite sides of the medium?
The reason for this question is that I was noticing how ...
- 39.6k
4
votes
2
answers
367
views
Can photons form a black hole?
Can photons form black holes the same way as other matter? If there happens to be enough of them concentrated in an area of space so that enough energy exists within a radius to form an event horizon, ...
- 1,496
1
vote
0
answers
29
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Parallax free projected image on diuelectric coated glass
I'm not a physician at all, just a computer scientist, so be nice with my average brain.
I'm working on an Optical System composed of:
A IR camera
A pico projector (TI DLP2000)
and a clear glass Anti-...
- 213k
2
votes
1
answer
376
views
Do gravitational lenses act as prisms?
Light creates gravity, and the greater the light's frequency, the greater this gravitational effect is. It stands to reason then that light of different colors would react slightly differently to ...
- 630
2
votes
2
answers
617
views
Can mirrors reflect destructive lasers or do they absorb the energy and would get destroyed themselves?
There is much talk of using lasers to bring down drones. That talk is followed by talk of protecting the drones by surfacing them with mirrors.
Would that work or does light falling on a mirror ...
9
votes
3
answers
435
views
Do gravitational waves change the color of light?
It stands to reason if gravity changes the color of light then the color will be affected by gravitational waves. My question is, when the waves pass, will the color change be permanent or will the ...
- 630
8
votes
4
answers
1k
views
Why can't thin clouds form rainbows?
Sunlight easily passes through THIN layers of clouds, composed of small water droplets/vapor, what is the problem accounted by the light rays that they are not able to form a rainbow?
- 1,270
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1
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79
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The angle of the prism for which there is no emergent ray will be, if its critical angle is $i_c$?
I read the answer here https://www.toppr.com/ask/question/the-angle-of-the-prism-for-which-there-is-no-emergent-ray-will-be-if/ . It said applying Snell's law at the two refracting surfaces,
$\sin i= \...
- 10.1k
5
votes
2
answers
161
views
Albedo of water vs temperature
This question arose out of pure curiosity.
Is there a relation between the temperature of water and its albedo? Would the albedo increase if I increased temperature? Say I measure albedo by directing ...
- 550
0
votes
0
answers
30
views
Do lightbeams redshift one another upon passing?
If it's true that anti-parallel light beams affect eachother gravitationally does this imply that they mutually redshift in addition to bending their paths towards one another? For example consider ...
- 630
-1
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3
answers
119
views
Why do images invert to create a perfect image (ie a pinhole camera)
This image has always confused me, and it seems to be the go to example when explaining why images are inverted when looking through a pinhole camera.
I understand that light travels in a straight ...
- 42.3k
1
vote
1
answer
131
views
What happens to light that never hits anything?
Im a blue collar worker, just had a thought. What would happen to photons that never hit anything. It must be possible that at least one photon out there somewhere just happened to not ever hit ...
- 45.7k
2
votes
2
answers
77
views
How can any object except Plasma emit white light or be a blackbody--it seems contradictory?
How can any physical object absorb and emit white light when all objects are made from atoms and molecules, each of which has its own absorption/emissions spectrum that acts as it's signature “...
- 65.1k
0
votes
0
answers
36
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Can the eye lens not produce a virtual image when the object is between Focus and Optical Centre?
My teacher dismissed the question saying it is not possible for the eye to do so simply because we didn't know the focal length of the eye. That confused me. The focal length can vary, sure. When we ...
- 58.6k