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

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246 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 ...
3
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2answers
286 views

Light and parabola

I know that parallel light beams hitting a parabola will be focused at the focus of the parabola (f = 1/4a) and a light source at the focus of the parabola will ...
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1answer
515 views

Why does the speed of light within a solid depend on frequency?

Different frequencies of light travel at different speeds through solids, which along with Snell's law allows for rainbows. Has this phenomenon of variable speeds been predicted through derivations? ...
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3answers
2k views

Why does light in a room not form constructive and destructive interference patterns?

This is something that I have wondered for a long time. How come when I walk around why do I not see random black spots where light has collided destructively and bright spots where it has collided ...
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2answers
10k 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 ...
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2answers
278 views

Microwave absorption in tissue

Why do I have a big microwave absorption in tissue, when the tissue conductivity is high? I thougt the opposite would be correct. Can somebody explain the reason?
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525 views

Electromagnetic-Radiation [closed]

describe how radiation from a resonant LC circuit is increased by opening out the capacitor plates? Explain that a straight wire provides reactive elements of a LC circuit.
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1answer
326 views

Over what distances can one send/ receive from a GPS chip implant in a dog?

I am not into all the tech details of communication via RF with implant chips (tracking chips) and so would like to ask how the known atmospheric pertubations of shortwave radio affect the distances ...
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1answer
579 views

Formula for polarized “light” transmission through close filters?

I'm still trying to understand photons (or polarized electromagnetic radiation). This question is similar to one of my previous questions, but different: Consider the famous demonstration of crossed ...
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2answers
159 views

speed of an electromagnetic wave

I have this equation $$\dfrac{\partial E_z}{\partial y^2} - \mu_0 \varepsilon_0 \dfrac{\partial E_z}{\partial t^2} = 0$$ Why is $v^2 = 1 / (\mu_0 \varepsilon_0)$ ?
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Exactly how is the constant measured velocity of light deduced from Maxwell's equation?

For electromagnetic radiation the velocity of propagation is $c = 1/\sqrt{\mu_0 \epsilon_0}$. Since both $\mu_0$ and $\epsilon_0$ do not vary in any inertial frame, then $c$ must be constant in any ...
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Does the absence of a sound particle indicate that there are no photons?

Sound is usually referred to as just "sound waves" - we do not talk about a "sound particle" and only as a wave or "matter wave." Could something similar apply to light i.e. that there really is no ...
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1answer
158 views

How colored light can be explained if light is considered as emission of photon?

If light is considered as wave, then different colored light can be explained as waves of different wavelength/frequency. How colored light can be explained if light is considered as emission of ...
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1answer
188 views

Scattering off a random magnetic field?

Here is another old exam question I'm wondering about: A proton moving in the $-x$ direction encounters a region of space with a magnetic field that randomizes the direction of the particle. The ...
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5answers
878 views

Should I cook two pieces of Canadian Bacon twice as long as one in a microwave?

It will probably depend on the size of the pieces... but at what point should I stop assuming a linear relationship? I was prompted to ask in a previous question.
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7answers
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Why does light change direction when it travels through glass?

This was explained to me many years ago, by a physics teacher, with the following analogy: "If someone on the beach wants to reach someone else that is in the water, they will try to travel as much ...
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2answers
204 views

Multiple channels of information in single electromagnetic wave?

I'm trying to understand how can multiple radio stations transmit information just by transmitting using different frequency. The way I understand it all those different frequency waves add up to a ...
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2answers
558 views

Is it true that any system of accelerating charges will radiate?

I was recently told by a physics teacher that "any system of charges in which at least some of the charges are executing some sort of accelerated motion, will radiate and lose energy". This refers to ...
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2answers
374 views

Waveguide and ethernet

I am having a doubt about waveguides and the traditional Ethernet cable. The newest Ethernet i.e. the 10Gbps Ethernet has an astounding speed of 10Gbps. Which consists of 4 lanes in Cu as physical ...
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3answers
829 views

Newtonian Bending of Light?

I ran across THIS Newtonian explanation for the bending of light. Does it have any merit?
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2answers
961 views

If you run an electric current through a wire loop, do the accelerated charges radiate?

Does an accelerated charge always radiate? For example the current electrons in an electric circuit when moving through a turn they are accelerated, do they radiate because of that acceleration? If ...
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0answers
155 views

Modeling a spray painted polyurethane surface reflection

I'm modeling light interaction/reflection from a fiberglass surface with polyurethane epoxy (that is very reflective) that has been spray painted with a matte black paint. I'm looking for some input ...
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4answers
2k views

How can a laser pointer have range of several kilometers in atmosphere?

Laser pointers manufacturers claim that some pointers have range of several kilometers. Okay, they use a powerful laser, but that powerful laser usually has power less than one watt. Okay, the laser ...
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1answer
4k views

Why are lasers inefficient?

Why are lasers inefficient? Is it because of the heat lost during lasing? Why couldn't there be thermocouples or turbines in parts of the cooling circuits to extract something out of that heat?
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2answers
197 views

Is there a reason for photodynamic therapy to not cause cancer if mobile phones might?

I don't want to open a debate about whether cell phones can cause cancer, I read the thread: Could cell-phone radiation cause cancer? For the sake of this question let's assume there's a chance for ...
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1answer
143 views

Does a slide in a projector act as a diffuser?

I was wondering whether or not a slide in a slide projector acts as light diffuser? So when I have a light source that does not have a parallel beam on the slide can I expect that the other side of ...
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1answer
332 views

Is there a limit to the visual information a photon can carry?

As photons bounce around and finally find their way into our eyes, are they continually relinquishing the information of the previous thing they "bounced off of"? Is this the reason why we receive a ...
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181 views

range of infrared light

I notice in the EMS chart that only half of the IR range will travel through the earth's atmosphere. So in the range of frequencies that penetrate the atmosphere what frequency travels farthest?
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844 views

Light Energy Absorption In Mirror

Let the amount of energy in one pulse of (laser) light be $E$, and the wavelength be $\lambda$. This pulse goes straight to the mirror, and it is reflected by the mirror. Let the reflectivity of ...
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2answers
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What does an electromagnetic wave look like at a fixed moment in time?

I am curious what the electric and magnetic field's of light look like when time is stopped. A "photograph" or illustration/description of these fields at a moment in time is what I desire. Also, ...
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4answers
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What happens to light in a perfect reflective sphere?

Let's say you have the ability to shine some light into a perfectly round sphere and the sphere's interior surface was perfectly smooth and reflective and there was no way for the light to escape. If ...
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7answers
5k views

Why is electricity not transmitted wirelessly?

Why is electricity not transmitted wirelessly such that we don't need to span cables on the earth's surface? As in: electricity is transmitted wirelessly from the power plant to the household.
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2answers
179 views

Solar chamber trapped light

Was wondering if trapping light in a reflective chamber could heat rods sufficiently enough to heat water? Trying to think of new ways in which we can utilise solar energy.
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5answers
800 views

Could cell-phone radiation cause cancer?

It is very crucial that I ask whether it ``could'' and not whether it does. I do not mean to be the least controversial. To my surprise, having read ``Physics for Future Presidents'' by Richard ...
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3answers
402 views

Could we enable ourselves to send messages to and receive messages from the future?

Based on John Isaacks' question, "If you view the Earth from far enough away can you observe its past?" and the responses, it appears that we could use mirrors to see into the past. Using Vintage's ...
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6answers
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If you view the Earth from far enough away can you observe its past?

From my understanding of light, you are always looking into the past based on how much time it takes the light to reach you from what you are observing. For example when you see a star burn out, if ...
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1answer
248 views

Why electromagnetic waves propagating along x transfers to electron momentum along z?

Why EM waves having only x momentum transfers to electron z momentum? Electron begins oscillating along z, so will not radiate EM waves along z direction, to compensate its z momentum. It seems that ...
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3answers
2k views

Batman spotlight in the sky

I have noticed that obstructing a spotlight typically results in a blurred shadow unlike the crisp batman symbol in the comics of batman. Is there a way to create a spotlight with a crisp batman ...
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1answer
300 views

Linear polarizer and the angle of incidence

It is known that when a beam of lineary polarized light falls perpendicularly on a linear polarizer, the intensity of polarization changes according to Malus' law and the direction of polarization ...
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2answers
707 views

vander waals and casimir forces

Does one need to invoke quantum mechanics to explain casimir force or vander waals force. I see that textbooks show derivation of vander waal force with no QM but casimir force is typically described ...
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3answers
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What other shielding material than lead is effective against gamma rays?

As the question in the title states I am wondering what material can be effectively used to shield gamma rays apart from lead? I believe concrete is often used, but it is nowhere near as effective as ...
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2answers
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How do you calculate the intensity of light around the focal point from a focused collimated beam of light?

Problem/Purpose of me asking this question to you people who know more than me: So I'm doing a science project where I'm collimating a beam of light to a focus point in a light medium (water vapor or ...
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0answers
129 views

Where does light energy go when the electric and magnetic components equal zero? [duplicate]

Possible Duplicate: Popular depictions of electromagnetic wave: is there an error? The electric and magnetic components of light increase and decrease at the same time, pass through zero ...
3
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3answers
159 views

Distant bodies emitting photons

This comes from a discussion forum, where a friend of mine asked the following: We can see objects in space billion of light years away, right? I started wondering about that. If you take 2 ...
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2answers
301 views

Effect of gravitation on light

Einstein predicted that the gravitational force can act on light. This was verified in one solar eclipse that light from a star near to the sun's disc bent due to Sun's gravity as predicted. Since ...
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1answer
171 views

Will the sun cool and produce a disrupting EMP?

Scientists say rare drop in sunspot activity could cause global cooling http://www.globalpost.com/dispatch/news/business-tech/science/110615/science-news-solar-flares-sunspots-global-warming ...
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1answer
1k views

Polarization and mirrors

When a light beam reaches a dielectric surface, the incident and reflected beams have different intensities depending on polarization. For the so-called Brewster's angle, the reflected light is ...
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2answers
427 views

How long do reflections take?

How long does it take for a photon to be reflected? Starting with the photon being absorbed by some atom to the point it's reemitted? And what's the same point with pressure waves, like sound?
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2answers
2k views

Michelson rotating mirror experiment

Could someone explain the calculation required to answer this question. It is from a text book and the answer is recorded as 585Hz but I cannot replicate the answer. In 1931 Michelson used a ...