Light Definition and 1000 Threads

Everything has the speed it's moving at , at the time it's measured . Light always leaves its Source at the speed called "c" . That doesn't mean its Relative speed is always "c" for all observers .

hello! I am trying to make a device that will improve reproduction rates in certain microorganisms that I am studying. They reproduce fastest under shorter wavelengths, specifically best at blue light. Any ideas for devices or materials that could help out would be appreciated! An idea I had was...

please be specific about the number of mirrors I have to use and how large they should be and what angles they should be placed at. And how much light and where should I shed. Thank you. I also made a stupid doodle which I thought might help

...but is it correct to say: Speed² (in space) + Time² (in space) = 1 ?? derived using Pythagorus (explained at 10-13 minutes in)....the trade off between Speed and Time, at maximum speed Time is zero and at max Time, Speed would be zero.

Hi PF, as far as my modest knowledge goes, measuring the one-way speed of light is impossible / non-sensical (?). Thus I'm not here to actually propose a possible method for that purpose, but I just would like the savvy among you to point out the fallacy in my reasoning. That said, I was...

Does light bend around black holes like a satellite "slingshotting" around Jupiter? If so, would there be a need to recalculate the true positions of stars from all the bending of light around black holes on the way to the telescope?

Each type of cell responds to light with wavelengths in a certain range. The distinct ranges center around yellowish red, green, and bluish violet, respectively. A "response" from a receptor cell is some neural signal to the brain. The combination of the responses of all our receptor cells...

Hi! (newbie here) I'm doing a experiment, very simple, in the center of a box there is a light source, a small one, and closer is a photon counter device. The challenge here, and the hard DIY part is the box. The box can not any photon get inside, nor emit any of them. At the same time it...

Is Geometrical Optics (GO) essential to fully appreciate the nature of light? I absolutely love Wave Optics (WO) and am currently studying it at the undergraduate level. However, GO feels more like an applied science, where I’m mostly dealing with the geometry of small angles. It doesn’t give me...

If a source emits a light pulse then waited one second and sent another pulse does the distance between the two pulses remain constant ? If yes is that mean their relative speed is zero? But why when we use lorentz transformation their relative speeds gives us zero over zero but if they travel...

I have a question regarding a light fixture I'm building that also has a motor in it. It has geometric shapes that spin slowly around the light (almost like a mobile) and this is what I'm using the motor for. The light fixture will be attached to the ceiling like any normal light fixture or...

How can the speed of light remain the same for an observer while the duration of a light beam is shorter if you move towards the light, and longer if you move with the light? The light beam remains the same length.

https://physics.stackexchange.com/questions/824561/two-element-theory

If you and your frame are following a square path in space, and the Universe is the other frame, each leg of the square path instantly changes every photon in the Universe to suit your dimensional perspective of speed, length, frequency, and time. Is this new light situation actually different...

Looking to see if I am in the ballpark correct about this. Let's say a spaceship flies at 99% the speed of light (B=0.99) to a planet 12 light years away. The spaceship is going to land on the planet once it arrives and stay put ever after. Ignore acceleration of start/stop. When it lands on the...

Hi everyone. I hope you are doing great . I recently saw something interesting and had a question. I use fluorescent lamps in my room, and when I use the remote fan, it works at a shorter distance, but when the lamps are off, the remote works at a longer distance. What do fluorescent lamps do...

Taking into account the Rayleigh scattering phenomenon, assuming that the atmosphere is 1 bar, how would the light from the G2V-type star interact with this kind of environment? Could the colour of the sky even alter despite the fact that there is a significant amount of sulfur dioxide in the...

my question then is that can we ascertain some unknowns about the physical constants of our universe by using video altered speeds , to observe the universe through moving picture frames ? Is there a project benefit in doing more with this ?

If I’m not mistaken, the synchronization of 2 clocks to conduct a measurement of the one-way speed of light is not possible since simultaneity is not possible and 2 clocks even if they are synchronized in a midpoint and slowly moved to opposite ends, depends on c being the same in all...

It's a question I've pondered over for years and I've even asked a few people but I've never had a convincing answer. As per the summary, if gravitational lensing is spraying light all over the place like an automatic lawn irrigator, is there any chance some light will do a tour of the universe...

I am interested in making an observation that involves the speed of light. It is widely stated that the speed of light is constant, but without saying what that means. I need to be precise, and would like a reference to an acknowledgement of the problem. When people talk about the speed of...

The caption says this volcanic 'light show' was caused from "an accumulation of static electricity". If that is so, I do not know the physical reason for that at all. Hopefully, someone can enlighten the ignorant. If it is something other than that, possibly, my guess would be that...

Does the product of Planck's Constant and the speed of light, hc, have any significance in physics other than an arbitrary product of two constants? I noticed that it appears in one formula for the fine structure constant. It also appears in Planck's formula for black body radiation. Thanks...

Is there an explanation for why the speed of light tops out at 186,282 miles per second? Of course that number depends on our definition of miles and seconds. If a mile was 3000 feet then c would be a different number. But whatever speed it is…. Why that speed? In other words… there is...

I had a rough night of sleep tonight and woke about 3:30. At one point I was awake on my side and noticed a small burst of light in the room, which I found a bit odd, being familiar with all the things that blink, etc., and not expecting any. But I figured it was just one of those. Then, about...

TL;DR Summary: This is an astronomy application. Mentor note: Moved from a technical forum section, so the homework template is missing. How long does it take a beam of light to reach Earth from the Sun when the Sun is 93,000,000 miles from Earth? Express your answer in seconds, using...

Who can help me to calculated a reflector for a straight light tube with a diameter of 6mm and a length of 300mm given a beam with a width of 100mm at a distance of 500-700mm?

Hello! I measured the light transmitted from a bow-tie cavity (while scanning the cavity length) and the peak obtained while scanning has the shape in the figure below. It is basically a combination of a Lorentzian, with an exponential decay on the right side and some oscillations on top. What...

Imagine there is an experiment setup on a train. A laser, with a specific wavelength of light, is aimed at a target. The target is at a distance from the laser of some multiple of the wavelength. Let's say 10cm for the target distance, and the light's wavelength is 1cm, so when a pulse of...

Hi. The numerical value of the speed of light ##c## pops out as propagation speed of the wave solutions to Maxwell's equations. It seems like everywhere else we need to plug in ##c## as a parameter. Why is that? Is there a way to "derive" the numerical value of ##c## in other theories, that...

In the 1934 novel by John Taine, Before the Dawn, scientists are able to retrieve images of the past by accessing the light absorbed by stones throughout history. While this is fictional, 1934 was really before the dawn of quantum physics. In the far future, could we retrieve images from light...

Kuusela https://research.utu.fi/converis/portal/detail/Publication/32053938?lang=en_GB (published in AJP) (PDF here) describes a pseudothermal light source that can be built easily in college labs, and can be used to do some quantum correlation experiments. They propose this as an alternative...

I don't know how to explain it in terms of speed. I know the speed will decrease but if the ray entering the glass at certain angle, let say 10 degrees, the speed will also decrease so what is the relation of speed to the fact that the light will bend or not when entering the glass? And the...

What I mean is that how would someone see light from something like a flashlight in a tunnel? The idea of light rebounding like a ball against a wall I do understand. What I would like to apply this to is graphics programming. the objects that I would simulate this for are puddles on the floor...

Can you explain this for my grandmother? Four years ago I rented an apartment for her on the 7th floor in a new building. I then decided to take care of my grandmother, so I lived with her. Everything was fine, but a year later the light bulb in the guest bathroom burned out. Since I'm the...

Twin Paradox. I am on the outgoing rocket and look back at my stay at home twins light clock (two mirrors with a ray of light bouncing in between) I get to the nearest star and on the outbound journey my twins clock apears to run slow. When I turn around my plane of simultaneity shift and I...

I must add, that, when used in a lit space, or in daylight, spraying before the mirror does not make any light rays visible. Is it simply a matter of light scattering? Also, I am not sure whether this question belongs here or in classical physics.

I am more so stuck on where to start with this problem. I know dividing the photons per second by the area gets me the photon per area, but I am not sure how the distance is related to this part of the problem. If anyone can help, thank you.

I think this is the appropriate subforum. I'm curious as to what approaches have been taken. I know this prediction isn't correct. I can think of at least a couple ways that I could go about this. They may or may not give the same prediction. One approach would be to simply use kinematics, and...

We see under trees circular light that goes from sun through the leaves gaps. Why does it create a circular shape and not other shapes? why does this diffraction phenomenon create it in circular patterns?

Looking at Kruskal diagram, it appears that light from all previous events of something crossing event horizon at that same point, reaches the falling observer when it crosses the event horizon. Is my interpretation correct?

What is the difference between space and vacuum? Since light waves require a medium to travel, then what is the medium in space?

Sorry for my questions as an amateur interested in physics: If light changes its frequency during a long time of travel in space (vacuum?) for all observers (redshift) and therefore its energy decreases (E=hf), what "entity" absorbs this energy? I suppose the answer will be that the wavelength...

I am aware of the explanation for light slowing down. From what I understand the EM field causes electrons in the medium to oscillate interfering with the wave and slowing its progress through the medium. The question I am asking is about a light source (or any source) that is turned on. If I...

I am looking for help getting started with focusing light into my monochromator. This is all just hobby level stuff with limited budget for high end lab gear. I have a 35mm slide projector I am going to re-task as a light source. It has a 200 watt tungsten bulb that is passed through a...

I approach a traffic light. It is red. I know it is a light. What is happening in my brain to inform me that I am looking at a red light, and not a brightly colored red circle on the canvas of my perceptions of the physical world? If my eyes are moist and I squint, I see radiating red lines...

I don't really have any idea. I know that shorter wavelengths refract more on entry to prism; e.g. ultra-violet refracts more than infra-red, but I don't know why they don't join up again when speeding up on exit from the prism.

I'm reading book from here. Suppose two rockets are accelerating with the same acceleration ##a## and are separated by some distance ##z##. At time ##t_0## the trailing rocket emits a light pulse. The book tells that pulse reaches leading box after time ##z/c## as seen in background frame. But...

Does it violate the postulate of special relativity in any sense?

If I start with a mix of half H2O and half D2O, when it equilibrates it will be half HDO, a quarter H2O and a quarter D2O. My question is "how long does this take?". Ballpark is fine - microsecodnds? Days? Centuries?