basic question about electromagnetic radiation

[nec4b]

Hi!

I know that in order to have EM waves propagation one needs an electron that accelerates. But light is also an EM wave and we can generate it just by using DC current. There is no acceleration going on in a LED or a bulb, so i guess you don't always need accelerating charge to get EM waves?

best regards to all

 

[rautio]

Good question!

The accelerating charges in the two examples you suggest are kind of sneaky.

For the light bulb, the electrons of the DC current bump into atoms and shake them around. This creates heat and electrically, we measure resistance. The acclerating charges are the jiggling atoms. The radiation is also known as "blackbody radiation". The sun is another good example of black body radiation.

For the LED, it is a little different. Electrons at one energy level fall down to a lower energy level at the PN junction. The tumble from one energy level to a lower energy level is the acceleration, and it results in radiation. Solid state experts (of which I am most definately not) can provide more precise details.

 

[VSMVDD]

the earth is a magnetic field so your right you dont need any form other than electron donation to take place {the human body emits light in many forms rf and volts even current can me measured from your body

.: light can also come from a chemical source like high power lasers protract there sources form its nice to note that

in laser light if you look at a spot from any laser device

youll see what appears to be a mush of red and black light
ye black light using a columbator you can study this light
as bands of black
with bifringance mixing you can modulate the black light

more research need dont into this phenomena

so even light dosnt need to be at-all visible
would be nice to see what em comes form laser light

after all some guy in the states is launching flying saucers into space with very powerfull pulse lasers

 

[nec4b]

Thank you both for your answers. It helped me understand EM theory better.

 

[azzouzkr]

I need an e-book or an article about the EM effects on human body.