Propagating solutions to Maxwell’s equations in classical electromagnetism and real photons in quantum electrodynamics. A superset of thermal-radiation.

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683 views

Does sending data down a fiber optic cable take longer if the cable is bent?

Ok, so, my simplified understanding of fiber optics is that light is sent down the cable and it rebounds off the sides to end up at its destination. Which got me thinking, if it has to bounce more ...
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1answer
682 views

Polarization rotation: Jones Matrix that maps Horizontal to right circular

I am looking at the Poincaré sphere and I am trying to compute a Jones matrix for a particular rotation. Specifically, I would like it to perform the following maps: $O :|H \rangle \rightarrow |R \...
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4answers
3k views

Some questions about car radio and cellphone antennas

1-Why the antenna of the radio of cars is located outside the car and not inside? 2-If the answer to 1 is because that cars are like Faraday cages then how come my cell phone can receive signal ...
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0answers
255 views

What is the electric field part of an EM wave? Radiation field or the induction field?

Look at this image: I wonder if the electric field is from the induction field from a vibrating electron or the radiation field? If it is from the radiation field, as I suppose, than can someone ...
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0answers
422 views

Cerenkov light - a practical calculation

I need to calculate the approximate total amount of energy radiated, via Cerenkov, by a muon as it traverses $10\:\rm{cm}$ of quartz glass. Unfortunately I've spent so much time fiddling with ...
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3answers
334 views

Light Rays that are Perfectly Parallel

I just heard this simple reasoning in a documentary film: Light rays from distant stars are perfectly parallel. This is pretty interesting thought. In nature, it is hard to find something really ...
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2answers
8k views

How to determine directions of vectors of an electromagnetic wave

I did an exercise which probably is quite popular, in which you draw an electromagnetic wave and prove that it should propagate at the speed of light $1 \over \sqrt {\mu_0\epsilon_0}$ using Farday's ...
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4answers
848 views

Electromagnetic wave reflection vs. light reflection

Related: x-ray interaction with atmosphere I know that electromagnetic waves of particular frequencies reflect from the ionosphere. And the light (which from one perspective is an electromagnetic ...
2
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2answers
439 views

Does EM radiation (any, i.e. RF), or sound, radiate everywhere at once?

I am having trouble understanding electromagnetic radiation (or waves in general, be it EM or sound). If I have a 1 Watt speaker, is it infinitely divided and spread out so that everyone in every ...
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3answers
5k views

Why is it necessary for an object to have a bigger size than the wavelength of light in order for us to see it?

I keep hearing this rule that an object must have a bigger size than the wavelength of light in order for us to see it, and though I don't have any professional relationship with physics, I want to ...
2
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3answers
666 views

Can a photon be emitted with a wavelength > 299,792,458 meters, and would this violate c?

Just curious if the possibility exists (not necessarily spontaneously) for a photon with a wavelength greater than the distance component of c to be emitted, and would this inherently violate the ...
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3answers
2k views

x-ray interaction with atmosphere

Why x-ray are stopped by atmosphere while they are more energetic than UV or IR? They certainly interact with atmosphere but I can't understand which phenomenon stop them.
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1answer
457 views

Peaks on top of Bremsstrahlung

The following is a graph of the intensity of Bremsstrahlung generated by accelerating electrons to hit a target vs. its wavelength. I'm wondering what causes the additional peaks for high energies? ...
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4answers
10k views

Understanding the diagrams of electromagnetic waves

I'm having trouble understanding the diagrams of elctromagnetic waves. I have no problem with any concept in classical mechanics, and I think this can be answered without any relativity (which I don'...
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2answers
3k views

Why can't electromagnetic radiation from magnets be used for apparent perpetual motion?

If electromagnetic radiation represents a transfer of energy, then does a permanent magnet represent unlimited energy, and if so, why can't magnets be used for perpetual motion? Even if permanent ...
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2answers
374 views

Is there a readily available (or at least not theoretical) material that reflects only infrared light?

By way of context, please picture those little motion capture lights that are put over an actors body. I am interested in finding out if there is some kind of material that can do the same thing but ...
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1answer
259 views

Reflectance of Round Moon vs Flat Moon

Treating the moon as an ideal, bright Lambertian reflector, I was trying to compare its efficiency as a light source to an equally-sized flat sheet of drywall. It's pretty straightforward to set the ...
0
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2answers
293 views

light travels a maximum speed… /? [duplicate]

Possible Duplicate: Is it possible for information to be transmitted faster than light? we know that speed of light is an unconquerable term in physics..light takes about 1 year to travel ...
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2answers
470 views

Working of a crystal radio

I have been reading about how a crystal radio works and I have one question below: It says, the energy in form electric current from a specific frequency will be stored in the coil (or a resonator) ...
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6answers
15k views

How many colors exist?

How many "colors" do exist? Our perception: As far as I know, colors are just different frequencies of light. According to wikipedia, we can see wavelengths from about 380 nm und 740 nm. This means ...
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3answers
24k views

Why don't electromagnetic waves require a medium?

As I understand it, electromagnetic waves have two components which are the result of each other, i.e., when a moving electric charge creates a changing magnetic field at point X then a changing ...
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1answer
2k views

How does a receiving antenna get an induced electric current?

From this question, I've noted that an electromagnetic field carries no electric charge but it has two components: Electric field Magnetic field Now what I failed to understand is how does the ...
3
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2answers
4k views

Why do electromagnetic waves become weaker with distance?

From what I know, In electromagnetic waves, the components electric field and magnetic field generate each other i.e. magnetic field generated from moving electric charge generates another electric ...
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0answers
145 views

What narrow-linewidth laser system runs at 2100nm with 1W of power?

For an experiment at our university we need a laser that runs at about 2.1 μm (about 20nm higher or lower would be fine too. We have found a multitude of lasers that achieve this (typically Thulium- ...
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3answers
5k views

How much electric charge do electromagnetic waves carry?

Since electromagnetic waves have both electric and magnetic field components, which oscillate in phase perpendicular to each other and perpendicular to the direction of energy propagation. How much is ...
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4answers
6k views

How does radio receives signal from particular station?

When you tune your radio (digital or analog) to receive say 100 MHz frequency and while in the environment there are hundreds of channels everywhere around the radio. How does it chooses to receive ...
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1answer
570 views

Can a big microwave used to dry clothes?

I was wondering if it is possible for a microwave in principle to dry clothes (assuming of course it is big enough).
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2answers
3k views

Wavelength-dependent refractive index

I read in a book about optical fibers that the different spectral components of a light pulse transmitted in the fiber propagate with different velocities due to a wavelength dependent refractive ...
3
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1answer
140 views

Is there any literature that compares the candle-power to the candela?

I am unable to find anything in the literature to back up the claim that appears all over the internet that: ...
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1answer
10k views

If microwave ovens and WiFi both operate on the same frequency, why doesn't WiFi cook things?

If we ignore 5GHz WiFi, then both microwaves and WiFi create photons at ~2.4GHz but one of them will boil water in a few seconds but the other doesn't have any effect. So what's the difference? Is it ...
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1answer
154 views

Is it possible to create a hologram using X-Rays?

Is it possible to create a hologram using X-Rays (or other penetrating EM-waves)?
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1answer
2k views

reflection, refraction and diffraction occur in radio waves, which one occurs the most?

One of the things about Radio waves is that they undergo different behaviors such as reflection, refraction and diffraction when in contact with obstacles such as walls, buildings etc. what i want to ...
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2answers
396 views

What frequency photons are involved in mediating physical force?

If the force felt when pushing an object is mediated by the electromagnetic interaction and hence photons, what is their frequency?
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3answers
2k views

Complex numbers in optics

I have recently studied optics. But I feel having missed something important: how can amplitudes of light waves be complex numbers?
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2answers
627 views

Near-field around parabolic antenna?

Having a discussion at work about the $H$-field around a big parabolic antenna. All of the safety tests done around the antenna only mention $E$-Field. They state in the radiating near-field the $E$ ...
12
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1answer
4k views

Can microwaves affect WiFi?

I listen to the radio via my iPad with wifi. When I switch the microwave oven on, the radio cuts out. When the microwave oven is finished, the radio comes back on. (This is 100% reproducible!) So - ...
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1answer
1k views

Absorption / Control / Reduction of EMF radiation using passive antennae & matched load

Wanted to understand the physics behind usage of passive antennae and matched load combination, to absorb, control and reduce the Electromagnetic-Field (s.a. due to microwave radiation from cellular ...
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1answer
474 views

Speed of Light, Photons or WaveSpeed?

The speed of light is almost 300 000 km/s. The photons have a speed along the wave, and the wave have a speed straight forwards. What is the speed of light? Is it the speed the photons have along ...
3
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2answers
2k views

What's it like in a sphere mirror? [duplicate]

Possible Duplicate: What happens to light in a perfect reflective sphere? I was working on my toy ray tracer when I pondered on this: Say we build a hollow sphere big enough to fit a person. ...
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4answers
433 views

Interaction of matter with EM fields

For the interaction between electromagnetic fields and matter, when do we have to include quantization of the EM field and when we can ignore it? when do we have to include quantization of atomic ...
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3answers
1k views

What does the differential of $d_s\sin(\theta) = m\lambda$ help us see, with respect to waves through diffraction gratings?

With respect to waves traveling through a diffraction grating, we have an equation like this one: $$d_s\sin(\theta) = m\lambda.$$ Where $d_s$ is the distance between slits in the grating, $\theta$ is ...
8
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2answers
925 views

Do gravitational waves slow down as they pass through matter?

I've heard that gravitational waves travel at the speed of light, and have some parallels to electromagnetic waves. EM waves slow down as they pass through matter (speed of light in glass is slower ...
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1answer
62 views

Is it possible to check from the EM waves(basically Light rays)?

Is it possible to check from the EM waves(basically Light rays), if there are any extraterrestrial objects interference/passage during its travel from the Sun? I mean, can these EMs from the Sun be ...
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2answers
237 views

Does light escape when I open my blinds?

When I open my blinds, there is light enough to read a book outside while the lamp is on inside. So when I close my blinds, does the light that otherwise will escape, stay inside and thus being ...
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2answers
267 views

Electromagnetic Radiation

If there was a way to see the electromagnetic waves that is all around us, i.e. see the electric and magnetic fields spreading away from an antenna say, how would it look? I mean if we were to freeze ...
3
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2answers
444 views

Big Bang and Cosmic microwave background radiation?

One of the experimental evidence that supports the theory of big bang is cosmic microwave background radiation (CMBR). From what I've read is that CMBR is the left over radiation from an early stage ...
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2answers
4k views

What is the minimum wavelength of electromagnetic radiation?

As a first approximation, I don't see how a wavelength of less than 2 Planck distances could exist. The question is: Are there any other limits that would come into play before that? For example: ...
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6answers
9k views

How to Make RF Waves Visible

I understand RF (Radio Frequency) Waves are electromagnetic waves and a mode of communication for wireless technologies, such as cordless phones, radar, ham radio, GPS, and television broadcasts. Most ...
2
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1answer
528 views

What happens to speed and frequency of a light beam moving in transparent medium when observed from different inertial frame of reference?

Suppose a transparent medium where speed of light is $c/n$, an inertial frame of reference $K$ which is stationary relatively to the medium and an inertial frame of reference $K'$ which is moving ...
5
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1answer
255 views

Is the number of wavelengths of light spanning a distance invariant with respect to spacetime distortion?

I was recently asked by a friend how the expansion of spacetime affects photons. I gave him what I feel is a satisfactory general response, but it got me wondering how, exactly to calculate this ...