Em wave Definition and 214 Threads

I am on Alpha 4 light years away from earth. On 1st Jan, 2016 I lit a powerful laser light towards Earth for 10 seconds and then switched it off. My friend on Earth knows that he has to detect that light after 4 years on the night of 1st Jan, 2020 from a space station using a very powerful...

Can the temperature of an object be derived from the EM Waves it emits? I know that everything having a temperature over absolute zero emits thermal radiations. The hotter the object gets, the higher the frequency of the wave goes. But for example if I have a hammer which emits a wave xHz...

Hi everyone, As we move from left to right in EM spectrum the energy EM wave carries in creases as does the Frequency. Then why even after having a lot of energy waves can't penetrate hard me trials like rock. For example, Microwave aren't that good in penetration of tough objects but have...

Although mass-less, a photon, like any other quantum particle, has a frequency/wavelength associated with its energy/momentum. If we have a group of photons all with the same specific energy, then each photon can be represented by a little, complex-valued plane wave. Photons are also EM waves...

Homework Statement A plane electromagnetic wave is incident on a material surface. The wave delivers a momentum ##p## and energy ##E##. Then which of the following is/are correct? 1) ##p=0,~E=0## 2) ##p\neq 0,~E=0## 3) ##p=0,~E\neq 0## 4) ##p\neq 0,~E\neq 0## Homework Equations None The...

Book says one of the properties of EM waves is they can impart momentum (and angular momentum)... What would be an example of this? (a simple example in terms of first year physics i mean)

In a vacuum, the plane wave solutions to Maxwell's Equations are... E=E0*cos(wt-kr) B=B0*cos(wt-kr) ie they are in phase. (See for example https://www.physics.wisc.edu/undergrads/courses/spring08/208/Lectures/lect20.pdf http://hyperphysics.phy-astr.gsu.edu/hbase/waves/emwv.html ) I don't...

Hi, I was able to correctly calculate the answer to part 1 below but the answer to part 2 is incorrect and I cannot see the error of my ways... any help gratefully received. 1. Homework Statement An electromagnetic wave has an intensity of 127 W/m2. 1) Find its rms electric field strength...

If I use 10mm (thickness) of a metal for the sides of a Faraday cage, with a 5mm skin depth at the frequency to be shielded, & increase the v/m of the EM wave to be blocked gradually, will there be a stage where the skin depth will increase to 6mm, or is 5mm the maximum limit?

Why can't we have an Electromagnetic wave in which the Electric Field and Magentic Field aren't in phase?

I know there is a pi phase shift when going from an area of lower index of refraction to higher. Is this phase shift still pi when going from a non-conducting dielectric with index of refraction n and reflection off a "good" conductor?

OK, I'm sure I'm just not thinking about this the right way, so please point out my simple mistake. Imagine a charged particle and 2 observers. Observer S is stationary relative to the charged particle, so sees no magnetic field from it. Observer A moves back and forth in front of the...

Given the following: A directional radio wave transmitting antenna which creates a beam (diameter in mm), a current in volts, and a frequency (Hz), is it possible to calculate the em wave voltage (v/m or w/m2) immediately next to the antenna? and then at a distance of 10meters? What...

The E and B field lines of a dipole radiating EM waves looks like that (sorry for the poor quality) : What I wonder is how can we see that the amplitude of the fields decrease as 1 / r? When you look as such a picture it actually feels likes the amplitude should rises. The E field gets...

Sources : paper here and http://www.quora.com/What-is-the-phase-of-the-EM-waves (fifth paragraph). This is beyond my knowledge so I am not looking for an explanation of the phenomenon. But I thought nothing could go faster than light so I am very surprised. Are there exceptions to the speed...

When EM waves interfere, what happens to the energy?

For a good conductor, an incoming plane electromagnetic wave will be attenuated exponentially as it penetrates a distance ##z## into the conductor, ##|\vec{E}(z)| = |\vec{E_0}|e^{-z/ \delta}##. ##\delta## is called the "skin depth". The current generated by this incoming electromagnetic wave is...

I'm so puzzled right now (sorry if I'm being stupid or something) , we can clearly see that EM waves oscilate the electrons in a conductor,they start vibrating and create EM waves again and these EM waves oscilate some other electrons and again they create another EM wave. All EM waves are...

How is energy dissipated in a traveling electromagnetic wave ? Will there be any dissipation if it were to travel through vacuum ?

With ω/k = 2π/T / 2π/λ = velocity for both transverse mechanical waves and EM waves. I can understand velocity as distance over time in mechanical wave. But how is the ratio Em/Bm = ω/k = c. That is the maximum amplitudes of the E and B fields in the y and z planes corresponding to c in...

Homework Statement Consider a particle of charge q and mass m, free to move in the xy plane in response to an electromagnetic wave propagating in the z direction (might as well set δ to zero) a) Ignoring the magnetic force, find the velocity of the particle, as a function of time. (Assume the...

this is theoretical (and possibly stupid) question; accelerating protons would create an EM wave equivalent to an EM wave generated by electrons at same frequency but the amplitude would be opposite, is that possible. has anyone made a communication circuit from accelerating protons? are...

When trying to explain reflection through the EM treatment of light waves, how do we account for the fact that the electric/magnetic field of the incoming light would penetrate into the medium from which it is reflecting off of? Diagrams like these: show the 'reflection point' on the axis of...

Homework Statement Hey, I've been given this EM-wave: (-2\vec{e}_x+2\sqrt{3}\vec{e}_y+3\vec{e}_z)E_0e^{i[\omega t-a(\sqrt{3}x+y)]} with a∈ℝ 1) Describe the wave and how it's polarized. 2) In what direction does the wave propagate? 3) What is the phase velocity of the wave? 4) What is the...

I know that in a vacuum, speed of light is constant. My question is more about the speed of light in a material like air. Dispersion of light in a prism tells us that the speed of light or the material index depends on the wavelength ( or frequency which is constant ) so I thought that air...

Homework Statement Consider a particle of charge q and mass m , free to move in the xy plane in response to an electromagnetic wave propagating in the z direction. Ignoring the magnetic force, find the velocity of the particle, as a function of time. Assume the average velocity is zero...

Why is gravity not electromagnetic radiation like attractive/repulsive force? I know the ans is related to shielding but I don't get it.

If I have a charge in a vacuum, and I accelerate it in a direction, then stop accelerating it, an EM wave will be produced for a short amount of time. How can you determine the frequency of the EM wave which is produced? Does it depend on the speed at which the charge moves? The amount the...

Do we say something is an EM wave only if the EM field is oscillating at a constant frequency? What exactly is the definition of an EM wave? If an electron moves in a direction and then stops moving, is an EM wave produced by that electron?

What experiments disprove the idea that light is waves of electromagnetic field?

For EM wave, magnetic and electrical components are in phase, meaning when E = 0, then B = 0. Thus, I understand if it is written: f(x,t) = A(cos(kx - wt) + icos(kx - wt)) Then why plane wave is always described: f(x,t) = Aei(kx-wt) = A(cos(kx-wt) + isin(kx - wt)) Implying that Real and...

A lot of electronic hobbyists would want to transmit information, signals through a medium other than the usual rope called wire or cables As this is a bit old fashion to have wires as a means of sending switches. So here let's share ideas on how to produce Electromagnetic wave... The only...

Quick question. If the EM field vectors are perpendicular to the direction that an EM wave is traveling, how can light push objects away from the light source, such as in the use of a solar sail?

Do individual photons have some attributes which relate to EM wave frequency? In other words, is there any difference in photons composing a red and blue beam of light?

Why do parabolic reflectors for microwaves (e.g. satellite TV) not reflect light like a mirror? Why do things like spoons, which are presumably conductive, reflect light? Thank you

Okay the question is, given a plane electromagnetic wave in a vacuum given by E=(Ex,Ey,Ez)exp^{(i(k_{x}x+k_{y}y+k_{z}z-wt)} and B=(Bx,By,Bz)exp^{(i(k_{x}x+k_{y}y+k_{z}z-wt)} , where k = (kx,ky,kz), to show that kXE=wB. So I'm mainly fine with the method. I can see the maxwell's equaion...

I'm going through my notes and I don't understand how they have included position in an equation to describe an EM wave. The equation is of the form http://upload.wikimedia.org/math/f/6/3/f6386c1751b91ec23c7123b15a11b52f.png [Asin(kx-ωt)]. This equation is just stated in my notes and there is no...

I don't really know how to quantify EM waves when it comes to amplitude, but I understand that MRI rf waves are measured in units of tesla. What is the amplitude of a typical microwave oven EM wave in Tesla (mT, uT)??

After reading Griffiths' book, I find the explanation from poynting vector to sinusodial EM wave pretty blurred. EM wave has two requirements. 1. E / B = c 2. E and B are sinusodial How could we ensure the Poynyig vector ultimately will produce the form satisfying the two points mentioned? Or...

From my understanding, surface plasmons (SPs) are oscillations of electrons caused by incident EM waves. A photon from the EM wave can couple with a plasmon to create a surface plasmon polariton (SPP). Some books/websites use the words SPP and SP interchangeably, so I am confused as to whether...

Homework Statement Show that the E and B field of a plane EM wave are both perpendicular to its direction of propagation in a non-dispersive and transparent medium. Homework Equations Maxwell's equatons.The Attempt at a Solution Well, I know how to easily show that E and B fields are...

Homework Statement The magnetic field intensity of an electromagnetic wave that propagates in vacuum is described with the following phasor notation: (H_{z} = H_{0}e^{+jkx}u_{z}) if the previous equation is hard to read maybe this will be easier: Hz=H0e^(+jkx)Uz. Assuming that the frequency of...

It is known that the electric field component of the EM wave is given by E=E_{0}cos(kx-\omega t) How do I arrive at such a form? It is quite different from the standard sinusoidal equation of y=Acos(\omega t+\varphi) Any guidance? What does the kx-\omega t describe physically?

i think I've asked this a number of times on different posts stemming from various discussions but i don't think this question was in the wrong thread. so I've decided to make a new thread for this. so what 'IS' an EM wave? i understand that the acceleration of charges could produce a wave...

i always hear about the frequency/wavelength, and the speed of the wave, but i never heard about the actual amplitude of the wave itself? how would one derive this? I'm not referring to intensity... intensity deals with the number of photons being captured by a detector... I'm referring to the...

Homework Statement A plane electromagnetic wave propagating in free space has an amplitude (\sqrt{3}/2)a_{y}-(1/2)a_{z} V/m. Find the amplitude of the accompanying magnetic field assuiming the frequency of the electric field is 1 GHz. Homework Equations f_{E} = f_{H}...

Hello, The energy density of an electromagnetic wave is ε_{0}E^{2}. To calculate the energy flux, at least in the derivation's I've seen, people just multiply by the speed of the wave, i.e., c. But doesn't this assume that the energy density is constant at all points?; but E changes...

Howdy everyone. 1. Ok, so we have and electromagnetic wave propagating through a vacuum. We know wavelength, and the magnitudes of B in the x and y directions. Also, B=[Bx(i)+By(j)]cos(kz+ωt). That's all the prereq stuff. 2. So Intensity is: <P>/A & (1/2)Bmax^2/Zo I'm def feeling...

Hello Everyone, I am making an LRC circuit by having a Coil attached to a Capacitor attached to a Light-bulb which is attached to the Coil. Provided that the radio signal (of 2000 Mhz) I'm trying to "collect" is strong enough and the coil/capacitor is properly tuned I should see the...

I am using "Advanced Engineering Electromagnetics" 2nd edition by Balanis AND "Antenna Theory" 3rd edition also by Balanis. I found an inconsistency in how to characterize RHC (CW) and LHC ( CCW) elliptical polarization. 1) In Advanced EE Page 159, for \vec E(0,t)=Re[\hat x...