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Author Topic: Why is sunlight called electromagnetic radiation?  (Read 6355 times)

Offline newspaper

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I was just wondering why is the sunlight called the electromagnetic radiation. I posted this on other science forum but got no satisfactory answers. MY friends even suggested me to look at some detail on quantum mechanics and gave me newbielink:http://www.physics-physicsdiscussion.blogspot.com [nonactive]. i also want to know if this site is useful or not.

newspaper,
« Last Edit: 04/03/2010 16:27:22 by BenV »


 

another_someone

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Re: Why is sunlight called electromagnetic radiation?
« Reply #1 on: 24/11/2007 15:51:04 »
Electromagnetic radiation is a term that encompasses a whole range of related types of radiation, from radio waves, through light, to X-rays and gamma rays.

http://en.wikipedia.org/wiki/Electromagnetic_radiation
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Legend:
γ = Gamma rays
HX = Hard X-rays
SX = Soft X-Rays
EUV = Extreme ultraviolet
NUV = Near ultraviolet
Visible light
NIR = Near infrared
MIR = Moderate infrared
FIR = Far infrared

Radio waves:
EHF = Extremely high frequency (Microwaves)
SHF = Super high frequency (Microwaves)
UHF = Ultrahigh frequency
VHF = Very high frequency
HF = High frequency
MF = Medium frequency
LF = Low frequency
VLF = Very low frequency
VF = Voice frequency
ELF = Extremely low frequency


You will notice that it is not only sunlight that is regarded as electromagnetic radiation, but all light, whether from a light bulb, from a camp fire, or from the Sun.

http://en.wikipedia.org/wiki/Electromagnetic_radiation#Theory
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Electromagnetic waves were first predicted by James Clerk Maxwell and subsequently confirmed by Heinrich Hertz. Maxwell derived a wave form of the electric and magnetic equations, revealing the wave-like nature of electric and magnetic fields, and their symmetry. Because the speed of EM waves predicted by the wave equation coincided with the measured speed of light, Maxwell concluded that light itself is an EM wave.

According to Maxwell's equations, a time-varying electric field generates a magnetic field and vice versa. Therefore, as an oscillating electric field generates an oscillating magnetic field, the magnetic field in turn generates an oscillating electric field, and so on. These oscillating fields together form an electromagnetic wave.

A quantum theory of the interaction between electromagnetic radiation and matter such as electrons is described by the theory of quantum electrodynamics.
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Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. This diagram shows a plane linearly polarised wave propagating from left to right.
« Last Edit: 24/11/2007 16:14:37 by another_someone »
 

Offline daveshorts

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Re: Why is sunlight called electromagnetic radiation?
« Reply #2 on: 25/11/2007 00:21:15 »
Basically light, ultraviolet, infra red, microwaves and radio waves are all the same type of thing, a wave. They only differ in how fast this wave is vibrating, light about 100 000 000 000 000 000 times a second an radio waves from thousands to millions of times a second.

The next question you ask about a wave is what it is a disturbance in, a water wave is a disturbance in the surface of water, a sound wave is a disturbance in air, and a mexican wave is a disturbance in people in a stadium. It turns out that light, radio waves etc are a disturbance in the electric and magnetic fields, so they are all called electromagnetic waves.

 This means that if you put something electrically charge or magnetic in the path of an electromagnetic wave it will be vibrated by the wave. So if you want to pick up a radio wave you use an aerial - a conductor with lots of mobile charges which are moved by the wave, this movement can then be picked up by the electronics in your radio and you can listen to it.

When it comes to light, because the vibration is so much faster you need a much smaller aerial, about the size of a molecule, so your eyes detect the light with special light sensitive dye molecules, which have charge that can be moved by the light giving them energy which through a load of complex biology triggers a nerve signal

I hope that helps
 

Offline newspaper

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Re: Why is sunlight called electromagnetic radiation?
« Reply #3 on: 25/11/2007 09:05:51 »
thanks for the reply but why did maxwell say that just because the equation which he took out met the speed of the light he concluded that this must also behave as a electromagnetic wave
 

Offline Soul Surfer

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Re: Why is sunlight called electromagnetic radiation?
« Reply #4 on: 25/11/2007 09:39:08 »
Because it also met all the other physical properties expected of electromagnetic radiation.  If it looks like a dog and barks like a dog it probably is a dog  :-)
 

Offline daveshorts

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Re: Why is sunlight called electromagnetic radiation?
« Reply #5 on: 25/11/2007 12:08:49 »
yes mostly inspired guesswork, later there has been lots of other confirmation, but Maxwell didn't know for sure at the time, he jsut thought it could well be the same thing.
 

lyner

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Re: Why is sunlight called electromagnetic radiation?
« Reply #6 on: 25/11/2007 16:21:23 »
Makes you feel humble, don't it?
 

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Re: Why is sunlight called electromagnetic radiation?
« Reply #6 on: 25/11/2007 16:21:23 »

 

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