sound needs medium to travell but please anybody can tell me that except sound wave any other wave like electromagnetic wave can generate through a speaker or a human sound in vacumm, any possibility is there that any specrum wave can generate though this?
According to me at least there should be a EM wave which is having wavelength equall to the sound wavelength.
@Yadav possibly em wave may be present which is very weak say radio wave as the case with fridge transformer etc. So wavelength may be somewhere in this reason.
I agree that the radiation is very weak. On the subject of the wavelength, generally the wavelength is lambda = v / frequency where v is the phase velocity of the wave in the respective medium. So, the frequency (or the spectrum) of the sound wave and the EM wave are identical but the wavelengths are not. For example, take a frequency of 1 kHz. The speed of sound in air at sea level is about 333 m/s; the speed of propagation of EM waves in air is about 300,000 km/s. So, the sound wavelength is about 0.333 m while the EM wavelength is about 300 km.
dear "Joerg Fricke" sir, i agree with your answer but i want to know that, is this em wave will be there just because of the sound wave or not. i am not assuming about there is any em source attached to the speaker like coil of speaker or current in wire.
No mechanical wave can travel in vaccum, that been said, a speaker generally have a coil and do generate electromagnetic waves in order to move the cone of the speaker, also almost every object (specially a living one like a human) produce termal waves, so, in summary, yes, there will be some waves been generated and transmited, but none of them are sound (you can extract the sound from the electromagnetic field of the coil if you work hard enough)
beste regards
Hi Ram Naresh Yadav,
apart from any "driver" of the membrane (or the vocal chords), if the oscillating bodies do not carry electrical charges (i. e. the sum of all charges is zero everywhere, in the macroscopic domain), then the oscillation will not cause EM waves, regardless of the surroundings (air or vacuum). If they carry electrical charge, then EM waves will be generated by the accelerating charge, equally regardless of the surroundings.
The only case I can think of where (partly) mechanical waves of the surroundings could produce EM waves occurs when the environment is a plasma with a spatially uneven distribution of charge, i. e. some kind of a ionized gas. But neither speaker membranes nor biological vocal cords will go well together with a plasma, therefore plasma waves are usually caused not mechanically but by (primary) EM waves.
thanks to all of you for your opinions on this topic.... some what about it really helps me...
thanks again...
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