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

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55 views

Can a combination of two or more x-ray type beams be made to burn tumours at their intersecting focal points inside a body?

A single x-ray or similar type beam can pass through a human body with little or no damage. Has anyone ever tried to use a second beam that is phased to have no harmful reactions with the tissue ...
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1answer
274 views

The electron jumps and lets loose photons

Where is the source of the photon. If the photon propagates from within the electrons transit does this point to some sort of field? Does the energy come from a boundary being broken in laymens ...
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4answers
4k views

Bohr's model of an atom doesn't seem to have overcome the drawback of Rutherford's model

We, as high school students have been taught that-because Bohr's model of an atom assigns specific orbits for electrons-that it is better than Rutherford's model. But what Rutherford failed to explain ...
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0answers
693 views

What is the attenuation spectrum of radio waves in pure water?

Here is a plot of microwave attenuation in atmosphere: (source) I'm looking for a similar plot, but for pure water, and a frequency range covering at least 100 MHz to 2 GHz, hopefully more.
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2answers
168 views

Could you make a bar of metal glow by forcing the charge density on the surface to oscillate?

Since light is just a changing electromagnetic wave through space, could you create light by changing a charge density at a certain frequency?
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1answer
42 views

Radiation from farther galaxies

I've read many facts from NASA's webpage.. Sometimes they tell, (for example) "NASA's Chandra X-Ray Observatory discovered this ultra-luminous X-Ray source (about 15 million LY) which shows an ...
2
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1answer
500 views

why is advanced radiation absent?

the Lienard-Wiechert green functions have future and past null cones of radiation. Maxwell equations allow for a continuous range of mixtures between the retarded and advanced components, but we have ...
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2answers
592 views

Counting electromagnetic modes in a rectangular cavity and boundary conditions

The electric field in a cubical cavity of side length $L$ with perfectly conducting walls is $E_x = E_1 \cos(n_1 x \pi/L) \sin(n_2 y \pi/L) \sin(n_3 z \pi/L) \sin(\omega t)$ $E_y = E_2 \sin(n_1 x \pi/...
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3answers
2k views

Can light exist in $2+1$ or $1+1$ spacetime dimensions?

Spacetime of special relativity is frequently illustrated with its spatial part reduced to one or two spatial dimension (with light sector or cone, respectively). Taken literally, is it possible for $...
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2answers
148 views

What is the history behind the factors of 3 in the classification of electromagnetic radiation?

What is the history behind the factors of 3 in the classification of electromagnetic radiation? See e.g. http://en.wikipedia.org/wiki/Radio_spectrum#By_frequency Is this (just) inherited from the ...
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3answers
417 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 ...
3
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2answers
92 views

limits on a gauss box of light

Consider a wall defined by $w(x,y,z) = \Theta(x-L)$ which is nonzero in the infinite semi-space of $x \ge L$, as well as a coherent planar standing EM wave travelling in the $z$ plane given by its ...
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2answers
115 views

What is difference between the miltary radar in 1940's from commercial antenna that is for the use of TV

What is difference between the miltary radar in 1940's from commercial antenna that is for the use of TV? I have read article from some of the WW2 history website that call the German radar the ...
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1answer
104 views

Is this claim from historician true for physicist point of view?

"The original Naxos I had a vertically polarized antenna, with poor results as the British radars initially used horizontal polarisation. (This seems to have been a case of the German designers being ...
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2answers
3k views

How do mirrors work?

My physics professor explained to me that electromagnetic waves are consisted of two components - electric and magnetic - which cause each other. Which part of the mirror actually reflects the wave? ...
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2answers
1k views

Why does laser light not affect glowing materials?

I have this childrens rubber ball which glows in the dark after it's exposed to light. I "charge" it with a flash light then play with my dogs at night. I thought to try a very intense green laser, ...
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2answers
798 views

Mean free path of UV photon

I was wondering if there's a simple way to compute the mean free path of UV photons in a optically thick medium with density n. I've looked up at the literature ...
2
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2answers
1k views

Magnet and energy conservation

If we consider a steel ball falling under gravity in a cup (potential well) and being stopped at the bottom by an obstacle then energy conservation implies that the gravitational potential energy has ...
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2answers
422 views

Liquid crystal polarizes light reflection question

I was hoping someone could help me with understanding why a row of polarizes reflects a light wave when the whole row is the same length as the wavelength of the light. I pretty much get the ...
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2answers
4k views

How to capture electomagnetic radiation/waves?

If I wanted to find out what kind of electomagnetic waves "travel" through my room at which frequency, what kind of equipment would I need? Suppose I want to view frequencies from 0 Hz to 6 GHz.
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1answer
712 views

Electromagnetic field of unpolarized light

I need help in finding an expression for the instantaneous electric and magnetic field of unpolarized light in order to write down and evaluate the time-averaged norm of the Poynting vector (i.e. the ...
9
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1answer
122 views

Wave Physics - can a dynamic waveform be constrained to a specific geometry by signal processing alone?

Suppose that you have a signal source, a set of point-transducers, and a handful of moderately powerful DSPs. Is it possible to construct an arrangement of the transducers such that the original ...
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2answers
105 views

Painting wine botles [closed]

Yes, it's a physics related question. Read on. I know from general knowledge that in order to produce a decent wine, you must keep it in a dark place. Therefore, from my knowledge of physics I guess ...
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0answers
102 views

what exactly do electric waves transfer from one point of the wire to other..? [duplicate]

Possible Duplicate: how does electricity propagate in a conductor? so basically i was considering the speed of the charges inside wire defined by the drift velocity and speed of electric waves ...
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2answers
555 views

PV cell for invisible spectrum only

Is it possible to make a photovoltaic cell that would only absorb the invisible part of the electromagnetic spectrum, while letting visible light pass through or bounce off its surface? I guess that ...
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0answers
480 views

Lorentz transformations of the polarization vector

Let $\bf{n}'$ be a unit vector in the direction of a wavevector in the plasma rest frame and $\bf{B'}$ be a unit vector along the magnetic field in the plasma rest frame. The electric field of a ...
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1answer
1k views

What are the optimal shapes, if any, for fractal antennae?

A DIY fractal antenna project is described at http://www.htpc-diy.com/2012/04/diy-flexible-fractal-window-hdtv.html Mainly idle curiosity, but I was wondering what the principles behind these might ...
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2answers
170 views

Radiative transfer equation solution

The solution of the radiative transfer equation for spherical ionized blob : \begin{equation} \frac{dI_{\nu}}{ds} = j_{\nu}-\alpha I_{\nu} \end{equation} and solution is (Ref: http://en.wikipedia....
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2answers
1k views

Frequency and wavelength of photons

I try to better understand how electromagnetic radiation works. So I have some questions. If an antenna emits at 100MHz (the charges on the antenna oscillate at 100MHz) what frequency will have the ...
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3answers
1k views

Distorted colors of Google StreetView photographs near electric power lines

This is a followup to my question: Cyclist's electrical tingling under power lines Some users presented a convincing picture that the electric shocks under power lines are primarily from the ...
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9answers
6k views

Why do we think of light as a wave?

I've read that light travels in a straight line and has a wavelength of 400nm to 700nm. But I don't understand why does it have a wavelength and what creates its wavelength? I agree with the concept ...
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2answers
3k views

Does infrared rays pass through polarized glass?

Actually I had asked in another post that "Does infrared rays pass through active shutter glass" but someone just commented that infrared rays dont pass through polarized glass. If infrared rays ...
4
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2answers
2k views

Make a semi transparent mirror with copper

The question: How would you make a semi transparent mirror (50% reflection, 50% transmission) with glass with a layer of copper. For light $\lambda$ = 500nm Try to be as realistic as possible What I'...
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2answers
325 views

Understanding Dynamic light scattering

I'd like to understand the physics of dynamic light scattering experiment. In particular I want to understand the basic relation between relaxation time $\tau_q$ and the diffusion coefficient $D$: $\...
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1answer
73 views

Weather Radar Interpretation - Radial Rays

I was browsing the NEXRAD radar feeds (I'm not an expert, just figuring them out) and I came across the following signature (visit the link to view the radar image) http://cl.ly/3n0y0p0g2M0K2B313g3U ...
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6answers
26k views

Is all kind of light same speed?

Is there any speed difference between blue or red light? Is there ever a speed difference? Or does all types of light move at the same speed?
2
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1answer
1k views

A two-level system absorbs a detuned photon. Where does the extra energy go?

Let's consider simple two-level system with frequency gap of $\omega_0$ between ground and excited state. Now, when we turn on external electromagnetic field with frequency $\omega < \omega_0$, ...
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2answers
148 views

The Synchrotron at Caltech

In the Feynman Lectures Vol. 1, it says that the Synchrotron at the California Institute of Technology is capable of producing electromagnetic Radiations with a frequency of $10^{24}$ cycles per ...
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3answers
12k views

How does the grid on the microwave oven window prevent microwave radiation from coming out?

If I look through the microwave window I can see through, which means visible radiation can get out. We know also that there is a mesh on the microwave window which prevents microwave from coming out. ...
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1answer
4k views

Light interference maximum and minimum intensity points

This is a very basic question, but I just forgot how to solve this. It's classical physics question. Suppose that there are two light sources. And some place away exists a screen. How do I find ...
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2answers
152 views

Gamma Ray Bursts

What is the maximum frequency of the Gamma Rays produced during supernovae? And how are these detected by telescopes without getting some serious damage done?
3
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2answers
2k views

Why is the atmosphere transparent in the visible spectrum?

One of the great 'coincidences' in physics is that the Sun happens to shine most brightly at exactly the wavelengths our eyes can see; it's an easy explanation that our eyes evolved to make the most ...
47
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7answers
7k views

Cyclist's electrical tingling under power lines

It's been happening to me for years. I finally decided to ask users who are better with "practical physics" when I was told that my experience – that I am going to describe momentarily – prove that I ...
0
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1answer
300 views

Rayleigh diffraction by circular aperture

I am a beginner to physics and would need an explanation on a statement in a book "Karttunen, Fundamental astronomy". In a section named "Rayleigh diffraction by circular aperture", author states: ...
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1answer
947 views

Relationship between classical electromagnetic wave frequency and quantum wave function + de broglie frequency

As it is. As I study through classical mechanics and quantum mechanics, I began to wonder whether there is a relationship between classical electromagnetic wave frequency and quantum wave function ...
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5answers
29k 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 ...
2
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1answer
409 views

How is it possible that we see light from shortly after the big bang?

How can astronomers see light from shortly after the big bang? How did we get "here" before the light that emanated from our "creation"?
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5answers
4k 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, ...
4
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2answers
5k views

The energy of an electromagnetic wave

The intensity of an electromagnetic wave is only related to its amplitude $E^2$ and not its frequency. A photon has the same wavelength as the wave that's carrying it, and its energy is $h f$. So ...
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1answer
116 views

$\mu$T in to $\frac{W}{m^2}$ (for interpreting EMF readings)

I am considering purchasing an EMF reader, to collect data about what is being thrown off of power lines and various other sources in the house to reach some conclusions. An issue is, the meter can ...