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

learn more… | top users | synonyms (1)

4
votes
1answer
97 views

Earnshaw Theorem for ionic solids

Is a single molecule of sodium chloride (say) or a cluster of molecules of NaCl unstable, although macroscopically NaCl is in fact, stable? How can I reason this based on Earnshaw's theorem?
5
votes
3answers
7k views

2 ways to generate electromagnetic wave

According to Maxwell's equations, accelerating charges emit electromagnetic radiation. According to Quantum physics, heating causes electromagnetic radiation too. These 2 radiations, are they ...
2
votes
2answers
71 views

How does electromagnetic radiation affect the velocity of a charged particle?

I've heard that the acceleration of a charged particle releases electromagnetic waves. So let's say there is a charged electron moving forwards in a region with a downwards magnetic field. If the ...
0
votes
1answer
50 views

Has someone measured that in the far field of radio waves, the electric and magnetic field oscillate synchronously?

That in near field both fields oscillating 90° displaced is obvious since in antenna rod a lot of electrons will be accelerated and and this oscillation of electric field is escorted by alignment of ...
-3
votes
4answers
3k views

How can light carry data if light has no mass, and data has mass? [closed]

Via a packet-switched network, like the internet, data is sent as packets (bits) wirelessly via radio waves with Wi-Fi, or 802.11g, etc. What my question is is this: Radio waves are light; light has ...
2
votes
1answer
27 views

Polarization of light for a fast moving observer

For a fast moving observer the frequency of light becomes shifted due to the (relativistic) Doppler effect. But what about the polarization of the light? Could it be, that e.g. circular polarized ...
0
votes
2answers
22 views

For a light of given frequency, what does the amount of refraction in a variable medium depends upon?

I want to know whether the amount of refraction of a given monochromatic light depends solely upon the density of the of the medium ( increase the density to increase the angle of refraction), or ...
2
votes
4answers
2k views

The rule breaker, emissivity + reflectivity = 1

If emissivity and reflectivity are inversely proportionate, why does glass have a high emissivity of around 0.95-0.97 as well as being very reflective for IR Radiation? normally it works but not with ...
7
votes
3answers
331 views

Is it possible to split a single light beam into two beams of opposite circular polarization?

A properly oriented calcite crystal will separate an unpolarized beam into two beams, one vertically polarized and one horizontally polarized. Other polarizers pass just one polarization and absorb ...
7
votes
3answers
894 views

Can polarized light be unpolarized again?

I was just wondering if there could be a process that could unpolarize polarazied light. Is that possible?
1
vote
0answers
29 views

Is my window's semi-transparency a consequence of elementary quantum mechanics? [duplicate]

Studying mathematical concepts of quantum mechanics, I have recently become familiar with the classical model of one-dimensional particle being scattered by a potential barrier. As a mathematician, I ...
0
votes
1answer
43 views

Amplitude of eliptically polarised light

In elliptically polarized light, can one define something called amplitude of Electric field? If yes, how do we determine it?
1
vote
1answer
64 views

Have we really measured the wavelength of light? [duplicate]

Have we practically measured the distances between the variations of electromagnetic radiations in space in nanometers or is it just theoritical because of calculations? Also the one who have marked ...
2
votes
0answers
27 views

What does electric field of unpolarized light look like when measured?

When we talk about fermions in mixed state, we say that their state can't be described by a wavefunction and just compute all the probabilities using density matrix. That's OK because the ...
1
vote
3answers
900 views

Exciting Surface Plasmon-Polaritons with Grating Coupling

I'm very new the topic of SPPs and have been trying to understand this particular method of exciting surface plasmons using a 1D periodic grating of grooves, with distance $a$ between each groove. If ...
2
votes
1answer
38 views

Can a magnifying glass work on EM radiation other than visible light?

A magnifying glass is a convex lens which allows us to bend visible light, thus the image of the object appears larger. My question is, can a magnifying glass work on the rest of the electromagnetic ...
0
votes
4answers
131 views

Why aren't we affected by radium?

1)We have radium clocks, watches, wrist bands and many things which glow because of radium but we know that radium is radioactive so why isn't it harmfull for us when in bands, watches etc. 2)Does it ...
10
votes
7answers
11k views

Electromagnetic fields vs electromagnetic radiation

As I understand, light is what is more generally called "electromagnetic radiation", right? The energy radiated by a star, by an antenna, by a light bulb, by your cell phone, etc.. are all the same ...
10
votes
6answers
2k views

Why Does Light Not Become Polarized In A Magnetic and/or Electric Field?

I am familiar with the Faraday Effect, but I remain confused as to why the electric and/or magnetic components of light do not naturally align themselves with a magnetic or electric field (in a ...
2
votes
1answer
124 views

If we go to space why isn't the temperature high? [duplicate]

We know that the temperature in space (which has vacuum) is low. If I go to space will I feel sweaty and hot or chilly? I think I will feel sweaty and hot because the radiation (UV, IR, etc) of the ...
2
votes
1answer
31 views

Microwave burns related to power per photon?

In wireless telecomunications we have multiple bandwidths being used nowadays: GSM 900Mhz and 1800Mhz, UMTS 2100Mhz, LTE 800Mhz, 1800Mhz and 2600Mhz, Wi-Fi 2.4Ghz and 5Ghz, (reffering to European ...
0
votes
0answers
36 views

Would an inverted design of a laser phosphor display (LPD) work?

Background info... It is my understanding that a laser phosphor display works by emitting RGB laser beams through a mechanism that cycles them in a pattern similar to a cathode ray tube. When I read ...
2
votes
1answer
56 views

Why does a real/virtual photon interact only with charged particle?

A photon is the force carrier of an electromagnetic wave and it consists of an electric and a magnetic field propagating through space at the speed of light in vacuum. It exhibits wave-particle ...
0
votes
2answers
67 views

Can a laser work forever if constant electricity is provided?

Can a laser work forever if constant electricity is provided? If we take a laser and provide it with constant electricity will the reactions in the semiconductor generate photons forever?
26
votes
5answers
13k views

Why glass is transparent?

Once I asked this question from my teacher and he replied "because it passes light", "and why it passes light" I asked and he said "because it is transparent". Same question again, Why glass is ...
5
votes
5answers
2k views

Producing photons with same frequency, different amplitude wave [duplicate]

I don't understand how two photons of the same frequency can have different amplitudes, neither how to produce them. I know that classically the square of the amplitude is proportional to the energy, ...
0
votes
2answers
79 views

Theoretically, is it necessary that if light passes through a glass slab, its intensity should decrease?

Is it necessary that for an E/M wave of given frequency which can pass through a medium of given refractive index, it should lose some of its intensity. Practically, this must be necessary because of ...
0
votes
4answers
97 views

Induction and electromagnetic fields

I've got a few questions on induction and electromagnetic fields. My current understanding of induction and electromagnetic fields is that, when electricity/current flows through a wire, it creates an ...
19
votes
2answers
9k views

How do Optically Active Compounds Rotate Plane Polarized Light?

I am not sure if this is more of a Chemistry or a Physics question, but in my Organic Chem class we discussed that chiral molecules will rotate plane polarized light. However, my professor did not ...
1
vote
0answers
13 views

Eddy currents are out of phase with respect to the field generated by a coil?

I have a coil from which a sinusoidal current (low frequency, few kHz) should generate a precise AC magnetic field in the surrounding space. Another coil intercepts this field and the corresponding ...
1
vote
0answers
42 views

Rotational Spectrum of a Diatomic Molecule

The rotational energy levels of a diatomic molecule are given by $$E_l=\frac{\hbar^2}{2I}l(l+1)$$ where $l$ is an integer. If the molecule is a dipole it can emit or absorb electromagnetic radiation ...
16
votes
5answers
16k views

Phase shift of 180 degrees on reflection from optically denser medium

Can anyone please provide an intuitive explanation of why phase shift of 180 degrees occurs in the Electric Field of a EM wave,when reflected from an optically denser medium? I tried searching for it ...
1
vote
0answers
40 views

The interaction between waves and particles according to their wavelength [duplicate]

Why do EM waves with a large wavelength like those in the red range (and radio waves) interact with particles less than those in the blue range? That is the reason why the sky is blue, is that right? ...
1
vote
1answer
29 views

In a noiseless environment, how accurate do today's transmitters send EM waves?

Suppose that there is no external noise in the environment. How accurate are today's TEM wave transmitters in such a case? So if we want to send $200\cos(1000\pi t)$, can transmitters send exactly ...
1
vote
2answers
91 views

Does a source emitting visible light also emit infrared, microwave and radio waves?

I have a bulb which is hot enough to emit visible light and obviously it's hot enough to emit radiation which lies before the visible light temperature i.e. radio waves, microwaves, and infrared ...
0
votes
1answer
85 views

Find the electric field of light due to an LED [closed]

This is a JEE mains question which neither me, nor any of my teachers can figure out. Help me here. "A red LED emits light at 0.1 watt uniformly around it. The amplitude of the electric field of the ...
1
vote
2answers
89 views

Why does the light instantly disappear when we switch off the source?

For example i take a box which is completely covered by the most perfect mirrors possible inside and inside that box i have a bulb whose bulb holder is also covered with the most perfect mirrors ...
0
votes
0answers
30 views

What have we built? A resonant loop antenna? Rhombic?

Some background, my partner and I have built an antenna we are supposed to characterize for an assignment, and compare it to physical predictions. However, we don't know what type of antenna we have ...
1
vote
1answer
65 views

Why particles don't lose mass when they radiate

Charged particles radiate when accelerated: in the rest frame of the particle moving with acceleration $\textbf{a}$ the amount $dW$ of radiated energy over time $dt$ is $$ dW \propto \textbf{a}^2 ...
0
votes
2answers
1k views

Does travelling light help us see past versions of an object?

I saw a passage in my son's homework book, constructing a scenario in which a person standing on a planet 65 million light years away from Earth, with an extremely powerful telescope pointed at Earth, ...
0
votes
2answers
166 views

How does Huygens Principle explain interference?

How exactly does Huygens theory about the propagation of wavefronts account for interference?
7
votes
2answers
332 views

Measurement of blueshift from Andromeda galaxy

How the blueshift from Andromeda galaxy was measured? Since the measurement of blueshift/redshift has to do with the identification of relative distance of spectral lines how this identification is ...
1
vote
4answers
144 views

Non-complex proof that the electric and magnetic fields are perpendicular in a plane wave

I'm looking for a proof that the electric and magnetic fields in a plane wave are perpendicular that doesn't invoke complex E and B fields. I haven't been able to find one. If the proof requires ...
6
votes
3answers
874 views

Why is it hard to detect a black hole

I've read in some texts that we can't directly observe a black hole in space because not even light can escape from its gravity. Some of the indirect observational methods mentioned are, gravitational ...
5
votes
2answers
655 views

Why do we use microwaves in microwave oven?

We know that any object above absolute zero emits electromagnetic radiation. So hotter the object shorter the wavelengths. In the electromagnetic radiation spectrum radio waves has the longest then ...
0
votes
3answers
75 views

What is the direction of the magnetic vector potential in an electromagnetic plane wave?

The vector potential $A$ is perpendicular to $B = \nabla \times A$, by definition, and hence, in a plane wave, it is either in the direction of $E$ or the direction of propagation. I suspect it is in ...
43
votes
3answers
6k views

Why doesn't light affect a compass?

In our daily life a lot of photons of visible light, infrared and radio etc move around us. We know that light is an electromagnetic radiation. So why doesn't that electromagnetic radiation affect a ...
1
vote
3answers
114 views

Why can't light escape a blackhole? [duplicate]

Gravity attracts objects which have mass right. We know that light is massless so why does a black hole's gravity attract light?
5
votes
2answers
213 views

Is it really possible to “discover” the speed of light with a microwave oven?

I've seen a number of sites/videos online that describe a method for measuring the speed of light, using a microwave oven and a chocolate bar. For example, this video on youtube. The basic idea is to ...
3
votes
3answers
290 views

How much of the universes mass is bound up in photons traveling between stars?

I was watching a Scott Manley video on youtube and he mentioned that the Sun was loosing 4 million tons of mass a second as it converts to energy. With a few trillion trillion stars also converting ...