Light Definition and 1000 Threads

I have seen many articles lately regarding planned manned missions to the moon and Mars but the question of radiation protection constantly comes up. Engineers keep proposing various shelter designs that use local materials (regolith) as a concrete base to absorb harmful radiation so that the...

How does the expansion of space cause light to lose energy?

How fast would the light travel for a SuperBig observer... immagine his head is the size of the Sun, and he is sitting in a room, then he decides to turn on the light in the room... if he is so big, would he have to wait some seconds until the light reaches his eyes? Would it mean that for this...

How does the sun emit or radiate its electromagnetic waves? https://imgur.com/odqclja Is it like the first picture where it might be spaces in between the waves or more like the picture under it where the waves are uni formally (I think is the right word) with no space in between them? Or...

First question: Within experimental error all measurements of neutrino and light speed in vacuum are consistent with c, but one way speed measurement of light is well proscribed, so is a one way speed measurement of neutrinos also proscribed? I have more questions, but maybe just clarify this...

Homework Statement I've just read that light can behave like a wave at times, and a particle at other times. How does the light from the Sun traveling towards Earth behave? A wave? A particle? Or both? And is it in any sense something that actually starts at the Sun, travels across space and...

If light speed (not in a vacuum) was about human walking speed ... Did any sci fi writer try that?

Drive two 15m long optical fibers extended in opposite directions with a 1GHz pulse generator. The recievers at the end of each fiber are now syncronised sources of 1GHz pulses. Connect them to pulse counters, one of which provides a signal whenever a pulse train is present. Connect this...

Why is the speed of light a constant?

I'm curious if car windshields / windows block UV (ultraviolet) light, the one from either the sun, or UV flashlights, like the Convoy S2+ Nichia 365nm.

Hi everyone First of all, I am a computer science student and I have a question regarding the polarization of light as stated in an article entitled "Multi-stage quantum secure communication using polarization hopping" by Rifai et al.,2015. Given the Mueller matrix: The input of light state is...

as we know light has momentum so theoretically we can use it but is it practical? (also this is it that light only exerts force if incident on something?)

By Uncertainty Principle speed of a particle cannot be constant. then speed of a single photon not?

Can an on board laser be used to propel a solar sail spacecraft if the laser is pointed at the sails ? Would Newtons third law affect the laser and maybe prevent the ship from moving ? Thank you for answering my very ignorant questions. NineNinjas911

if speed of light were not 3*10 ^8 m/s and something else would it affect the reality ?

Homework Statement The problem I have been working with recently has been deriving the speed of light using maxwells equations, however in order to do this I must make two assumptions; there is no net charge or displacement currents in the space in which I am attemptin to derive the speed of...

I did a little more research, please clarify. So the electric field is directed to the proton and that emits light? Can you get into more detail? I am not educated in math so this is hard to understand at this point. I understand how electrons emit light but not protons. So is the magnetic...

I remember reading about how a city could be seen across a sea at certain times. But normally would not be seen because of Earth's curvature. At certain times however, it could be seen because of light bending. I can't remember what the cause was though. Anyone know about this and what caused it?

The Faraday effect is a magneto-optical phenomenon caused by the interaction between light and a magnetic field. Is there a corresponding electrical-optical phenomenon, caused by the interaction between light and an electric field?

The speed of light from a moving source of light is usually recognized indirectly, based on various explanations of phenomena. The speed of light is fairly simple directly measurable on the basis of autonomous and separate measurements of the frequency and wavelength of the light. Is a similar...

Let us imagine a photon circling around a black hole, as the picture shows. The gravity of the black hole curves the movement path of the photon into the shape of a circle. From point 0, geometric points A and B appear simultaneously with the photon, each in its own direction. The points travel...

It had previously been verified within our own galaxy. http://uopnews.port.ac.uk/2018/06/22/einstein-proved-right-in-another-galaxy/

Glass allows visible light to pass through I would like to find a list of materials that allows lights of different EM spectrum to pass through, not just the above, Searched throughout google, couldn't find any!.

Hi this is my first question and love these Forums. I have a Independent research task due next term. My idea was: Seeing the change of wave length of light as it passes through different substances. My question is: How do i measure the wave length? Because I could use a spectrometer but my...

Homework Statement Homework EquationsThe Attempt at a Solution This is an example given in the book . But I am just wondering whether the question itself is correct . How can intensity of light emitted from Sun is given a constant ? Shouldn't 1400 be the power emitted from Sun ? If 1400...

The way I understand this is that Relativity says space-time is like a field that's affected by the way mass moves through it. Photons are massless so is this why the speed of light is the same in all reference frames?

Good morning everyone. I have a question for the community. I am doing an optical project in which I need, as the title says, to concentrate white light in a very small point, with a diameter of the order of microns, so that I can pass light through a pinhole. I've been trying it with some lens...

Suppose for the sake of argument someone said the outward speed of light is infinite and the return speed is c/2, creating a two-way speed of c. Wouldn't this violate the conservation of momentum? p = E/c. That means on the way out, the momentum of light would be zero, but on the way back it...

Homework Statement One 18 watt lamp and two 60-watt light bulb are plugged into a 120V circuit. For either DC or AC, the two bulbs are connected each other in parallel and in series with the lamp in the same circuit. Calculate; i. the current flow through each light ii. the total...

I am reading Feynman's book on QED and something struck me about light. I know that we can only calculate the probability of where a photon goes. After that I came across how a partial reflection affects light. My question is, is there a place in the universe where there is a great thickness of...

I am looking for an IR camera that can pick up 1550 nm IR light source on the pix level. I have silicon wafers and I am going to hit the pixels with a 1550 NM IR light source and I want to be able to see the pix with a IR cam. I want to connect it computer and use a C# application to view the...

Homework Statement Light of wavelenghs 4.80x10^2 nm and 632nm passes through two slits 0.52 mm apart. How far apart are the second-order fringes on a screen 1.6m away? λ₁ = 4.80x10^2 nm = 4.80x10^-7m λ₂ = 6.32x10^-7m d = 0.52mm = 5.2x10^-4m n = 2 L = 1.6 Homework Equations (Maxima/Bright)...

Hello, I have a question or perhaps a few questions regarding light and mirrors. When we point light at a mirror, it gets reflected back. But we can see the point light (assuming that it is a laser for the sake of simplicity) at a surface opposite to the reflective surface of the mirror. What...

Hi - I'm working to accumulate data on photosynthetic flux saturation levels across a range of plant species, and am having a bit of trouble understanding this paper: https://onlinelibrary.wiley.com/doi/epdf/10.3732/ajb.94.8.1344 Table 5 shows PPFD vs. ETR, and shows photosynthesis saturating...

Does anyone know the speed of light in dark matter?

I'm reading Special Relativity by TM Helliwell and in it he describes the second postulate and the fact that moving with respect to air changes the speed of sound, and that because light doesn't need a medium it's speed is constant. I remember my physics teacher saying that light itself(EM...

My question is about why the frequency of light or another EM wave does not change while passing through a medium. We know their Speed decrease and wavelenght change but think about this analogy for ex i am 4 meters high and drop 5 balls in 5 seconds and my friend waits at ground he will receive...

I recently saw this question on a forum thread on The Guardian's website but was unable to follow it up. Question: Why is the speed of light what it is? Could it have been another velocity?

If a pulse of light, which has momentum p = E/c, interacts with particles of air, would it not change their momentum over time, causing mechanical energy (sound)? As I understand it, sound is mechanical energy moving through particles as they vibrate. Why can't the momentum of a pulse of light...

Hi all I have struggled with the assumptions that the speed of light is absolute and constant. I have some logic to this which is based on the common assumptions that light behaves both as a wave and a particle. It is also based on light having mass, the effects of heat and vacuum environments...

After getting through a heat wave this weekend I've decided it's time to look at getting a ceiling fan for our bedroom. Right now there is just a simple light fixture. When I talked to my dad about it, he had some comments that made me realize it's not a straight swap. My house is year 1922 btw...

Suppose there is a screen. This screen has been divided into a very large number of pixels. Each pixel has a material, that has the capability of producing a potential difference when light falls on it. The potential difference for different wavelengths should be different. Say, over a range of...

Let's say I have an apparatus that's set up like this Let's also say that the mirror is infinitely long. If the mirror starts moving at subluminal speeds in the x axis, what would happen to the path of the ray of light? Would the dot made by the ray of light on the wall go up?

If a car drives on the highway at a speed of 100 ft per seconds and a gun in the car shoots a bullet forward at the speed of 1000 ft per second the total speed of the bullet will be 1000 + 100 = 1100 ft per second. If a car travels at the speed of light when you turn on the head lights will...

Hello everyone, I'll go straight to the question. The gravitational time dilation is equal to tearth = tspace*sqrt(1 - rs/r), with rs = 2GM/c2. However, the formula for speed of light in gravitational field is equal to v = c(1 - rs/r). My intuition tells me that these two formulas must be the...

In discussion with my friend, we reached a conclusion that transformation formula of velosity v to another IFR moving V, i.e. v'=\frac{v+V}{1+vV/c^2} is valid even if v is hypothetical velocity,i,e, v=\frac{x_2-x_1}{t_2-t_1} v'=\frac{x'_2-x'_1}{t'_2-t'_1} where interval of ##(t_1,x_1)\rightarrow...

So for some reason, from time to time, i always come back to this question and i can't remember that part of the physics while i was studying and most of the explanation are pretty generic. Basically how do we know that light actually travels and not just oscillate and transfer energy when...

Are there any relationships between the speed of light and the virtual particles in the vacuum? I mean that, Can I call it as a medium of propagation of a light beam?

As a neophyte when it comes to the relativity solutions I have been surfing the web. I came across something in Science Forums. <speculative link deleted> I have now become interested in what gravity does to light. My understanding of the post above is that the reference frame for light...

Before quantum mechanics, light was generally seen as a wave and matter as particles (biliards). From e.g. the discovery of the photoelectric effect, one saw that light can also be seen as a particle. From e.g. the double slit experiment, one makes the interpretation that matter can also be seen...