Em waves Definition and 234 Threads

Why do longer wavelengths spread out more than shorter wavelengths? What is the physics principle/law which explains why radio waves spread out more than optic waves in free space?

We can't see objects from objects far away from us. Why? I think light waves damps! When it reaches our eyes it's amplitude is too small to be visualised! Is this true? If indeed EM waves are damped then why? If not please give a suitable definition for the mentioned phenomena too !

There's a long conductor carrying a 60 hz AC current. There's a second conductor parallel to the first current carrying conductor, and a hundred meters away from it. I want to know what the electric potential induced by the changing B field is in the second conductor. Theoretically I could...

So i know that magnetic field lines are closed, in an electromagnetc wave how can be these lines closed? i cannot picture this in my head

Hey, guys. We all know power of AC currents is transferred via EM waves, but we seldom use that to calculate power in AC system. The reason for this is wavelength is very long. I want to know if there is really existed a transmission line which is 500km, just the length of EM wavelength, then...

Can you help me on this question I had for years? Every time I touch two metals together (holding them with my fingers) and place a shortwave SSB radio nearby, I hear clicks and noises on the radio. Why is that happenning? Has anyone observed this phenomenon before?

So far I have came to know that when a charge is accelerated the electric field magnitude around the charge changes and the effect is not felt instantaneously. The change in magnitudes of electric and magnetic field travels outwards at speed of light creating the so called EM wave. So the EM...

I've always read in my Physics textbooks that high energy EM waves like x-rays and gamma rays, if our body is exposed to them for a long time, can damage the skin significantly. However, how does that happen at an atomic level? As far as I'm concerned, the thing that differentiates a high...

An EM wave is nothing but just magnetic and electric fields regenerating each other. Now if a charge oscillates and it produces sinusoidally varying magnetic field which induces an electric field perpendicular to it at the same place.This induced electric field even varies sinusoidally thus...

Hi, I'm taking an undergrad course in Electromagnetism and Optics, and in the lecture notes it reads: "Consider the formal equation ε0D⋅E = 1 ... that must be obeyed for waves traveling in different directions as defined by the wave vector k but with a given energy density." Could anyone help me...

What is it about the em waves that get absorbed by electrons compared to em waves that traverse solid material.What is it about that wavelength, or frequency of light, and other em waves that get absorbed by electrons, that makes visible light get absorbed by electrons. Why that specific...

Hi, light as an EM wave attributes wave-particle duality. In general, are the other bandwidths of EMW (UV & IR for example) qualifies the same duality? How? Why and why not?

A comment a lab script for a recent experiment I did noted that the mechanism by which reflection of EM waves occurs is through the induction of Hertzian dipoles in a material. Having read up on Hertzian dipoles, I have found nothing which discusses them in the context of reflection. I read...

Guys, I am studying about electromagnetic waves and I'm not able to differentiate between a photon and a em wave or I'm not understanding it. Please help me to solve it out. Thanks

I wanted to know if my reasoning is considered sound, and if not please tell me the loopholes you can observe. The energy density in an EM field is (Its not necessarily a plane wave we're talking about here). ##u= \frac{\epsilon E^2}{2}+\frac{B^2}{2\mu} ## The relationship ##E=cB## is...

Matter has a wavefunction associated to it. But what about light? Does it have both a electromagnetic wave described by Maxwell's equation and a wavefunction described by Schroedinger's equation? Or is the electromagnetic wave considered to be the wavefunction of the photon? I read somewhere...

Hi... If we consider propagation of sound through a medium other than vacuum, we mean, when sound is produced by a vibrating speaker diaphragm, it gives periodic jolts to the molecules and atoms present in the medium or air. These "pushes" are transferred to all adjacent atoms until finally few...

I'm a high school physics student. I want to do an experiment to see what happens when a high frequency alternating current goes through a magnet. To create the high frequency alternating current could a photo resistor do that for me? Does the photo-resistor create an alternating current with a...

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?

Does an accelerating charge, such as one turning a corner emit an em wave or just a pulse? Classical logic dictates it should just be a pulse as there is no oscillation. But which is it?

Are the E and M components of an E-M wave (at a given frequency) necessarily in phase in free space? A conductor? A dielectric material?

Homework Statement I am just wondering is there any apparatus available to produce EM waves of arbitrary wavelength and intensities? If not, how I can produce an EM wave of my desired wavelength in the laboratory? Homework EquationsThe Attempt at a Solution I completely have no idea :(

Is there any star systems (planetary) that are influenced by the EM Force, hence as usual,sum of the charges of elements in the universe are electrically neutral.

Homework Statement Write down the equation for a plane wave traveling in perpendicular to the plane x+y+z=constant traveling in the direction of increasing x, y, and z. Homework Equations From the given information how do I determine the unit vector that goes next to E(0)? How do I determine...

Homework Statement The problem I have is that we are asked to show the complex relative permittivity of a good conductor is erc = 1 + i(sigma)/(omega*epsilon_0) where sigma is the conductivity and omega is the frequency of an electromagnetic wave in the medium. This is fine, I calculated it...

I've recently learned about EM waves. One thing I find hard to really get, is how the E and B fields are constantly "generating" each other. I think maybe the key for this is in the following equations, obtained from Maxwell’s equations in vacuum : (source...

I have several questions about the scattering of light. Air molecules scatter sunlight and makes the sky blue, many books say that the air molecules are oscillated by E field and so they becomes sources of EM wave. Is it because the air molecules have charges? I wonder if air molecules or...

From a textbook I read something like this: "When sunlight is reflected from a horizontal surface, the plane of incidence is vertical, and the reflected light contains a preponderance of light that is polarized in the horizontal direction... The manufacturer makes the polarizing axis of the lens...

For electromagnetic wave if it's reflected from a perfect conductor standing wave can be form. I wonder why Poynting vector can be used to describe the intensity of standing EM wave. (see p.19 of http://web.mit.edu/viz/EM/visualizations/coursenotes/modules/guide13.pdf ). From some textbooks...

According to Max planks equation, E=h*f, the more is the frequency the more is the energy of the EM waves. So why UVC (shortest uv ray or high frequency uv ray ) is absorbed by the ozone and UVA and UVB rays ( longer uv rays than UVC penetrate the ozone and reach the Earth's surface?

I am curious on what is meant by amplitude in an EM wave. From all the searching I have done the amplitude has something to do with the density of photons in the EM wave, and the frequency with energy of the photons. The part I am confused about is the fact that the wave is oscillating. I...

Hello folks. This is Sandeep. I have many lingering doubts in physics that I am here to get cleared. This has become more of an issue ever since I decided to teach physics to my young nephew. My first question pertains to electromagnetic waves and the conservation of energy. Consider an AC...

nothing in the universe moves without force, so what does makes em waves move through space?

I understand that sinusoidal EM waves result from charged particles in harmonic motion, e.g., up and down an antenna. But what if the charge is undergoing some more complicated periodic motion? Wouldn't the EM waves be non-sinusoidal? I saw in a textbook a hypothetical EM wave with infinite wave...

I have a question about complex reflection and transmission coefficients. For example, I am modeling a wave in air (medium 1) ## \varepsilon = \varepsilon_0 ## reflecting on, and transmitted to, a medium 2 with ## \varepsilon = \varepsilon' -j \varepsilon'' ## If the wave would have traveled...

I am reading through my course guide and problems worked out and something bothers me. I think at this point we are working with classical waves, moving towards QM eventually. The idealization we work with is this. We have a light source creating a wave ψ(x,t)=Acos(ωt+kx) . The light beam...

Homework Statement I've not been able to do this question for years so I'd really appreciate some help. Light is normaly incident from a medium 1 with impedance Z1 through a layer of medium 2 of thickness L and impedance Z2 into medium 3 of impedance Z3. Obtain an expression for the total...

Which of the following of a wave can be affected by the medium it travels through? (i) wave crest velocity, (ii) wave frequency, (iii) wavelength

First, some background. In Faraday's law the reluctance/resistance by "mother nature" to changing the magnetic flux is explicitly recognized by the "-" sign (commonly referred to as Lenz's law), i.e. if the time rate of change of the magnetic flux is positive, an emf is induced so as to oppose...

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 We have an infinite plane of width 2b made of a magnetic, conducting material (μr >> 1, σ >> 1). Two monochromatic electromagnetic plane waves, with magnetic excitation vector amplitude Hs approach it, each one traveling towards one of its two faces. Find the current density...

hi, everyone I didn't know where to post this thread so I posted it here. I have read many articles about EM wave to find what I'm searching for and nothing still. I have seen many pictures, animations and videos about EM wave, and about oscillating charge, but still nothing. What I am really...

Today, I made the following question at Physics SE, but the community redirected me here In short, I have made a proof for EF/MF phase difference near an oscilating dipole that "vanishes" far away from the dipole. So, what I am asking for is a proof verification. The physics SE post...

Why are electric and magnetic fields in an electromagnetic wave in phase? Can somebody please explain that?

Homework Statement Sphere of a radius R=50 cm is in nonmagnetic medium of permittivity ε=4. EM wave with amplitude of electric field Em= 200 V/m is spreading through the medium. How much energy pass through surface of sphere through 1 minute? I have couple of question here. Since the sphere...

How high frequency makes waves dangerous for us.also does all em waves have same speed of light?

Radio or any other wave in electromagnetic spectrum? Sound perhaps? And at what frequency(ies)

I understand that reflection of EM waves is the electrons on the surface of an object being caused to oscillate, and transmission is the electrons all the way through the object being caused to oscillate. Why, in reflection, when the electrons on the surface of an object are caused to...

EM field strength dies quickly with distance, what's so special about going up and down that allows EM waves to maintain their energy over infinite distance?

Is it one wavelength of EM wave? I have googled for this and I can't find an explanation for what a photon is in terms of EM waves.