Light Definition and 1000 Threads

I actually am not sure what equations are relevant here but I thought these are the relevant ones. My Approach: By Stefan-Boltzman Law, the intensity absorbed by the Earth is given as ## I = e \sigma T^4## where e is the emissivity of Earth, ##\sigma## is Stefan-Boltzman constant and T is the...

Hello I am not a physics student and i don't know anything about science, but i was curious if someone could tell me about what happens when light approaches a black hole i have heard that nothing goes faster than light but i have also heard that black holes can suck in light, combined with the...

I am looking for in an equation that's spits out the degree of polarization of reflected light, with incidence angle and the refractive indexes as inputs. an article online article had this graph decribing the degree of polarization as a value between 0 and 1 plotted against the angle of...

It has been put to me that a simple spectroscope could in theory demonstrate the isotropy of the speed of light . By using a frequency standard (laser comb or Th Lamp for example) with the spectroscope in various orientations the lack of shift of the spectral lines would prove its isotropic via...

Let me clarify my question, is there any experiment directly proved the invariance of light speed to observers? Let's not get to the argument of equivalence between source and observer. SR was based on the postulate that the light speed is constant and independent of both the motions of source...

The only knowledge I have about such reflection questions is theta=2theta. But I missed class when this was thought. Please I need help and guide

When using the voltmeter and ammeter to investigate the circuit, it was found that the batter had a current of 0.67 A, the two 30 Ω bulbs had a current of 0.17 A, and the two 10 Ω bulbs had a current of 0.50 A. In terms of voltage, each bulb had a voltage of 5 V. When the switch was closed, the...

Yess! speed of light it's driving me crazy. I know it might sound too noob and silly but please enlighten me, First of all how does we concluded that speed of light is constant for every observer in all possible inertial frames of reference. Next thing how come a photon doesn't experience...

Is there a equation for the speed at the end of the whip. is there a consistent way to calculate how fast the tip of the whip will be including constant velocity and trajectory or is it chaotic. Im new to physics and had a thought that with enough legnth and power a wiphs end colud reach the...

AM/FM radio stations, cell phone towers transmit signals at certain frequencies. How can the frequency of a signal change depedning on whether the receiver is moving towards or away from the source? I thought that the frequency of an electromagnatic wave is determined at the source (the energy...

Velocity of photon allways is c(photon is massless particle).While velocity of EM wave in medium < c.So does velocity of photon need not allways equal velocity of EM wave?

A point source of monochromatic light is placed in front of a soccer ball and a screen is placed behind the ball. The light intensity pattern on the screen is best described as: Answer: a dark disk with a bright spot at its center and bright rings outside Why is there a bright spot at its...

Good evening, I have a question on a cosmology problem I have solved from Barbara Ryden’s Introduction to Cosmology 2nd Edition. I believe I have answered the question correctly, resulting in the following linear redshift relation when using separation by variables and some algebra manipulation...

Hi all, I need help understanding the light ray bending in the original GR 1916 paper, Die Grundlagen.... First of all, Einstein states the ##c## is not an invariant in GR. In fact, from (70) and (73), it stems that $$\gamma = \sqrt{ -\frac {g_{44}}{g_{22}} }, $$ where ##\gamma## is ##|c| <= 1##...

Two 95 W (120V) light bulbs are wired in series, then the combination is connected to a 120 V supply. How much power is dissipated by each bulb? Answer 24W I followed the explanations as such: r1 = 120^2/(95) = 151.8 R = 303 r2 = r1 W = 190 I = P/V I = 190/120 = 1.58 v1 = 190/1.58 = 60 p1 =...

Based on Maxwell equations, we can determine the speed of light as: $$c=\frac{1}{\sqrt{\epsilon_{0}\mu_{0}}}$$ Where ##\epsilon_{0}## is the electric permittivity of vacuum and ##\mu_{0}## is the magnetic permittivity of vacuum. This notation makes me believe that in other mediums those...

Suppose that we tangentially send a light from an orbit of radius ##h## to another orbit of radius ##l## near a black hole. I would like to calculate the distance that the light travels. I start from the Schwarzschild metric, $$ ds^2=-(1-\frac m r) dt^2+\frac 1 {1- \frac m r} dr^2 +r^2 d \theta...

Light speed is impossible for anything with mass as more and more energy is required with increasing velocity. But this is only to an observer in a different reference frame. To the moving object, in its own reference frame, why would anything change regardless of how close to c it moves?

The twisted light propagate in curved line, then does twisted light violate Ferma's priciple?And then it violate refraction and refractive laws?

In a diffraction grating experiment, what can be the sources of error and also what effect do these sources have on the unknown quantity (wavelength) in the experiment?

Hello, If I shine a red laser onto a white surface, I assume that: some of the red light will be nearly instantly reflected, some will be absorbed and converted into phonons and some will be absorbed and re-emitted. Is that correct? I know that my laser has this extremely narrow spectrum...

Ok, so where do I begin? So I'll try to make this as short as possible sparing you all my issues. I like thinking about what is. My math takes me as far as pre-calc, but have no training in this field. I have the utmost curiosity in understanding the functioning of everything. Specifically...

There are 5 fantastic videos in this website: http://www.alfredleitner.com/ He is a very good educator and it is also very good to see those authentic experiments and aparatus. Anyway, in the following one at exacly 8:00 minutes he says that the phase lag induced by the dipole is always 90...

This post builds on a previously closed thread here: https://www.physicsforums.com/threads/lightbulb-paradox.141191/#post-1145674 I will not describe the problem here without the copyright owner's permission. I, like the OP in the original thread, am keen to see if anyone else who has this text...

what is wrong with the thought experiment below?! If I consider a light beam going straight towards an observer in motion it makes it look the moving clock ticks faster, but if you use a light clock it makes it look like the clock turns slower. What am I missing here? “Two observers convene in...

Hello All, I have a snowmobile that uses a shunt type regulator to control voltage. They require a constant load (headlights) to work proper. The 2 stock bulbs are 55 watts on low with the system running 12v. Racers install another set of hand warmers, wired to high, and tape them to the...

A thought experiment: A electron is moving in a straight line at velocity v. It instantly stops dead. It doesn't move another femtometer. Obviously its magnetic field collapses and produces light. What is the waveform of the light produced? Is it something like this...

Why do we know the velocity of all photons are the same as the velocity of light?Can we deduce this or we must have experiment test?What is the experiment test?

Hi. This is an idea which I just happened to think of, and I was curious if it would be at all feasible. Here's a quick sketch I drew: The two curved mirrors should have a laser attached on one end and a video camera attached on the other. The laser would be tilted very slightly above...

I read that our telescopes pointing in any direction show light coming from the early days of the Big Bang (like 13.7 billion years ago). So did the expansion of the Big Bang to "fill" the universe happen faster than the speed of light?

Question: Can heavy objects be used to operate light waves with smaller amplitude, or waves with high amplitude be used to operate objects with small mass? This is a diagram I drew that illustrates my point. Heavy objects are meant to be celestial bodies, and the light source generates a beam...

Here is the video: What is the physical explanation to why I see the light make patterns strikingly similar to magnetic lines on that spinning electric fan, depending on how I move the point of view? (the phenomenon happens equally to the naked eye and to the camera).

With this light clock delta t' in S' would be 2 Ls proper time. Since time measurements were done in same location delta x'=0 . Then from stationary S frame delta t = gamma delta t' . With gamma equal to 1.25 then that is 2.5 Ls. However the path the light takes as calculated from S frame in...

Hi bear with me I have a conundrum I want to ask you. If data traveled many times the speed of light could the results of decrypted cypher message be computed quicker than any system we currently have? For instance if we sent a burst of data at many times the speed of light across the solar...

Physics is not my area of expertise. That being said, philosophy of science is, but I'm not here to discuss philosophy. I recently found myself trying to imagine how light behaves once it crosses the event horizon of a black hole. Presumably, between the event horizon and the singularity...

Are the following statements true? --------------------------------------------------------------- If a speaker and a listener are stationary with respect to the air, a listener will measure the speed of sound at about 343 m/s. Since the speed of a sound wave in air is dependent only on the...

If time for something approaching the speed of light will slow down and approach zero, then how is it that light itself can exhibit changes - the oscillation of the E and B fields? Is it because those fields are perpendicular to the direction of light travel? If so, then something other than...

c^2 * t^2 = x^2 + y^2 + z^2 = r^2

its has been said that light slows down in glass, but some talk about phase velocity and group velocity... then there is the velocity of the photons, which some say is always c. What are those speeds [Vgroup, Vphase, Vphoton, Vlight] in glass, and what do they mean?

Hi Pf I read that in the light propagator there are loops of electrons. What would be the consequences if we could switch them off (or neglect them)? would it modify the speed of the photons?

I don't think this is what is observed, so where is my understanding wrong?

i made a simulation of waves in glass and in air. my simulation has led me to believe that if light begins in glass, it can travel to the air, and then move much faster, and then go back into the glass at a point further down. Could this happen in real life? here is the video of my...

https://www.allaboutcircuits.com/textbook/alternating-current/chpt-14/circuits-and-the-speed-of-light/ Sorry, my other post must have been too brief. In another thread shut down by Dale, this very site (allaboutcircuits) was used by him to reference wave guides. This particular page is 100%...

https://www.allaboutcircuits.com/textbook/alternating-current/chpt-14/circuits-and-the-speed-of-light/Hmmmmm. :))

as I read here http://www.bbc.com/earth/story/20160429-the-real-reasons-nothing-can-ever-go-faster-than-light#:~:text=But%20light%20is%20made%20up,when%20particles%20like%20electrons%20cannot%3F&text=The%20natural%20energy%20they%20possess,are%20already%20at%20top%20speed. things with mass...

Theoretical experiment for measuring one way speed of light From 1905 to this day we have not experimentally measured the one way speed of light between a source to the detector only the roundtrip from the source to the detector and back again. We just assume that the speed of light is the...

N1sintheta

I am asking this question in behalf of my father ( who does not have an account here to ask this question himself). My father said he does not understand why a simple light bulb in an AC circuit does not draw far more amps than a simple light bulb draws. He thinks that a typical light bulb...

I'm probably am wrong in this but i guess you guys could light me in this one

Suppose that we shined a source of light on a wall with infinitismal small opening. As the opening is infinitismly small, only one ray of light will pass through the opening ( suppose it has an intensity ##I_0##) and this ray of light will diffract into an infinite number of light rays with the...