Light Definition and 1000 Threads

Some people thought light speed is actually instantaneous which can be demonstrated by doing an experiment involving a taut clothesline and two clothespins. On each ends of the taut clothesline, put one of the clothespins on both ends and touch one of the clothespin will make the other one at...

Summary:: If relativity causes wavelengths to change I.e the redshift effect (or blue shift effect for objects moving towards us) does the presence of 7 different colours denote seven different changes? If the doppler effect shows that direction of trajectory changes wavelength and colour of...

In Richard Feynman's book "The Strange Theory of Light and Matter", in chapter 2, he explains how to calculate the probability that light from some source will be reflected by a mirror and be detected at some location. He explains how you sum up all of the probability amplitudes (represented...

In particle terms I'm thinking this could be when the signal's photon density drops low enough to be indistinguishable from the vacuum energy. In wave terms, I'm thinking maybe either the amplitude or frequency might drop below any quantum threshold needed to budge an electron shell in any atom...

Do you have accessible web links discussing the pros and cons of the various theories of light propagation in dense media? I have done quire a bit of searching, but all seems rather superficial (Don Lincoln's video, f. ex.) Thanks

Let us consider a hypothetical scenario, where we are able to translate any mass at a constant speed of 10m/s w.r.t to a given frame of reference. For simplicity, we are going to assume that the object is at rest initially. Case 1 - Now, consider 2 points A and B at a distance of 10m, and our...

The universal speed limit is c, and as a consequence light is confined to that limit. I was thinking about the time dilation in SR and was wondering if this is result of reaching speeds close to the speed of light or because of reaching speed close to c? For example, let's say light could be...

Hi Folks, I promise there is an actual question at the end of this note. I couldn't see where to attach images on this forum page, so here is a link to a rough illustration and a photo of the project site in progress (the cabinet for the digester is partially built)...

I watched a Fermilab video on light propagation in water: . He says (~) at time 7:50: "The oscillating electric field of the light make electrons in the glass move. These set up a second oscillating electric field that combines with the first to make a single oscillating field. That is the wave...

Can electromagnetic radiations exist on their own without any source (i.e light existing on its own without flashlight). If light can't exist on its own so sources are necessary for light or any EM radiations in order to exist, how about the EM fields?

Here is a concept suggesting reactionless drive: Setup: A light pulse of wavelength l0 bouncing between 2 mirrors one on the left - ML and one on the right - MR. Each mirror oscillates perpendicularly to light travel direction attaining relativistic speeds vl, vr. Light pulse is timed so it...

This is one of my thought experiments where I am drawing a big blank, If you have 2 objects approaching a 3rd object from opposite directions (just enough off to avoid collision) at 75% of the speed of light, the first assumption is that each observing the other would see the other object...

There are actually several questions. The formula for calculating the "beam angle" of light (emitted from lights bulbs, flashlights etc) is - α = 2 arcCos ( 1 - Lm ÷ ( 2 π Cd )) Where, α = beam angle in degrees Lm = luminous flux (Lumens) Cd = luminous intensity (Candela) The above formula...

In the screenshots below there are the equations (11.49) and (11.53). I don't understand how did he derive equation (11.53) from Eq.(11.49)? From (11.49) I get: ##d\phi/dy= d\phi/du du/dy = (1/b^2-u^2+2Mu^3)^{-1/2}(1+2My)##. It seems he neglected the ##2Mu^3## since ##Mu\ll 1##, so ##y\approx...

Since an object's apparent mass increases as it approaches the speed of light, does it's gravitational forces also increases? (From a stationary observer's point of view)

I don't need equations, I would just like to pose a question which contradicts the above statement (I know I am wrong btw, I want to see where I am going wrong).My understanding of space (not near any gravity and therefore no spacetime curvature) is that a body in motion will continue to move at...

Light emitted by a star should be gravitationally red shifted by its own mass, resulting in greater red shift of light emitted by a more massive star. Is this phenomenon known? Could this be contributing in Hubble 's law in some part too-- probably more distant stars are more massive too-- just...

I was reading Einstein's 1911 paper named "On the Influence of Gravitation on the Propagation of Light" when stated the formula for frequencies measured by observers at different fixed positions (heights) on Earth surface. One observer is at the origin of some coordinate system and measures a...

But then I learned a photon can be split into two or even three photons (red-shifted, energy is conserved), and also photon can lose energy and still be a photon (Raman effect, inelastic scattering). Now, I am not sure what it means when it is said photons are quanta of light (smallest unit of...

I've trying to explain this to myself but I know I'm missing something. I tuned the low E string to B. The frequency of that note is about 62 Hz. When I play that note under the led lights in my backyard I can see the string oscillate back and forth. After doing some reading, the LED light...

If a spaceship travels near the speed of light, could the frequency of cosmic background radiation blue-shift?

So I drew the problem and tried to derive t1 for an external observer by making the following assumptions. Inside observer sees light travel a distance of d0 meters in t0 seconds at a speed of c m/s. Bus moved Δd meters in t1 seconds at V m/s. Outside observer sees light travel a distance of...

To an average person with high school math knowledge how would you explain in a few words why no object could travel faster than the speed of light ? Well it's because...

A wavefront is defined as a surface in space where the argument of the cosine has a constant value. So I set the argument of the cosine to an arbitrary constant s. ## k(\hat{u} \cdot r - c t) + \phi = s ## The positional information is is in r, so I rearrange the equation to be ## \hat{u}...

I would like to know how to calculate, for any specified frequency in Hz, the required diameter of a 90 degree phased, quadrature coil array such that its generated EM field achieves rotation at the speed of light. Could someone please provide an example of the calculation using a specific...

If you measure the light transmission over time of the human thumb you can get the heart rate. Is there another thing you can get by using light transmission ? like the Heart rate? can you find bacteria in water using light transmission ?is light transmission measurement even the right word ?

Would an observer many light years from Earth (and approaching say) see events leading onwards through time (to what level of detail i am not proposing but say weather and maybe Humans on the ground?) in the light received?

However I need to know whether Planck also had to assume that emitted light was quantised to make his model work? I need to teach this topic in the context of how different experiments shaped our understanding of the light model. I have found 2 sources which seem to contradict each other:(...

When light originating from a medium of lower refractive index reflects off a surface of higher refractive index, why does the phase shift by 180 degrees? Stokes relations show that reflection coefficients at the surface are equal but of opposite signs depending on direction of light (i.e...

So recently I watched a video detailing how it is impossible to measure the speed of light in a straight line because it's not possible to synchronize two-time measuring devices without first knowing the speed of light. But I was thinking if light can orbit a black hole in the photon sphere...

I am aware that a laser could be modeled as a Gaussian beam, e.g., $$E=E_0\frac{w_0}{w_z}\exp (\frac {-r^2}{w^2_z}) \exp (-i(kz+k \frac {r^2}{2R(z)}-\psi(z))).$$ Now I want to study the propagation of light emitted from stars. But I am not sure how to model it, especially by some kind of...

Someone asked a really interesting question on a comment thread somewhere's, and ever since, I could never really stop thinking about what the proper answer to it could be. It's a really basic question, but it unpacks a can of worms. The exact question I read was the following This question...

Hi, I am looking for a suitable method to couple light from 2 LEDs into a fiber and then join both fibers, so that I only have one fiber at the end so that both wavelengths can be emitted from a single fiber. The first coupling step from LED into fiber seems to be more easy, I already heard...

The book says the actual measured deflection from some experiments is about ##9\times 10^{-6}## radians, and this is double the value that a naive computation returns because of general relativity effects. So I guess my goal is to compute a number that looks like half that. If suggests to do it...

Can light make two pairs? (assuming enough energy to make two pairs) If so, why? or If not, why not?

Your guys really helped me out with my last bulb problem so I thought I'd try again. There's a bulb over a staircase that is - a recessed floodlight - about 18 feet above the stairs directly beneath it (it's over the bottom of the stairs, and the staircase is exposed to the next floor) About...

Hi so to those of you who don't know the problem here is a video that explains it very well. - I have an idea on how to measure it, can someone please tell me if, and why it is incorrect. Thank you! Okay so we will have a timer, and a lot of mirrors, set up in a circle, a light beam is fired...

Hello, hopefully the question made sense, it was hard to translate. i attached a photo about the question. I started with n1=1.4, sinΘ1=37◦ and n2=1.62 1.4(sin(37◦))=1.62sinΘ2 1.4(sin(37◦))/1.62=sinΘ2 arcsin(0.52)=31.34◦ Is it calculated correctly?

My name is Dilip (James) I am fascinated by physics and have written three books on the subject, which indicates my level of interest.. My latest book “The Electromagnetic Universe: A New Physics” is available on Amazon and describes in detail: a new theory on the propagation of light, a new...

Say we just created a particle (high probability of one-particle state), is the probability of a very far away detector getting triggered at the time of creation (probability of finding a particle outside of its light cone) zero according to QFT? Since we can detect particles and make...

Because if stars are radiating light in every direction, shouldn't there be light all over? And we only see the light/photons that our eyes are receiving? Though there may be dark spots from where crests meet troughs? Or am I completely wrong and missing something?

Hello! I recently came across the Hanle effect, which is a reduction or increase in the polarization of the emitted light from an ensemble of atoms as a function of an externally applied magnetic field. Not so long ago I heard about the Faraday effect which is a rotation of the polarization of...

I am currently performing some experiments to calculate the distance between a light source and a lux meter where the light source points directly towards the lux meter. Is it possible to calculate the exact distance between the light source and the lux meter given that we have a lux value...

I am practice stick fighting for self defense. I have a question I don't know how to judge. Say if I have a 6oz and a 12oz stick both 28" long. I swing them to hit an object, assuming I have the same strength, obviously the velocity is faster with the lighter stick and slower with the heavy...

Can someone give a meaningful explanation that the relative speed of two oppositely directed light beams is why only one light speeds? I understand that based on the Einstein relativity theory, the relative speed of two beams is C, because nothing can be quicker than light speed. However it is...

Are there any materials that go from transparent to opaque when a bright light is shined on it? In particular I would like something that acts like a window until I project a movie onto it and then is opaque in the regions where the light hits it at certain levels of brightness.

Hello everyone, Preface: I'm hoping this doesn't violate the speculative or personal theories clause in the forum guidelines. It's really just a curiosity, I'm in no position to argue/develop/push the idea or anything. If this does violate that clause, would you be able to recommend a similar...

In every article that I've read about optical interferometers they explain that collimated light from farther the telescope is sent down the delay line, and then into a beam combiner with other beam. Like in the photo below But they all only show light that enters the telescope along the axis...

Hi, I have just now started learning about quantum mechanics, and I have an Idea, which i am 99 percent sure is wrong, but i wanted to post it just in case. Okay, so I researched it a little and it turns out that the probability for a single particle to experience quantum tunneling is 0.1%...