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Light only seems to last forever because our main light source (the sun) is so far away that it does not matter if the light has to travel one metre or one mile more or less. It is different when you have only a candle (for example). You'll have (barely) enough light as long as you remain close to the flame, but the intensity of the light decreases as soon as you go farther away. In fact, the intensity is inversely proportional to the square of the distance; at twice the distance the intensity (per unit of surface illuminated) will be reduced to one fourth and so on.It's the same with sound. Your ears are maybe about 50 cm from the keys on your keyboard, but if you move up to 5 m, the sound level of the click you hear will be already 100 times less.
I think there's a difference.As light is an electromagnetic wave it can propogate in a vacuum and go a very long way... Look up at teh sky at night and some of those stars are thousands of light years away. There is of course a loss of intensity with distance, but stars avery very bright. Now consider a LASER beam shining up into space, it wouldn't see the same inverse square law for loss of intensity as it is a collimated beam - within the diffraction limit anyway. This is why it is possible to shine a beam at the moon and measure the reflected light. In theory a photon of light could go on 'forever' provided it didn't hit anything.Sound is different. You hear sound beacuse of movement of air molecules. It is possible to focus sound to overcome the inverse square law but as a sound travels it will decrease in volume as the process of transmision of sound through a gas is 'lossy' - it is not 100% efficient. Eventually it will reach an intensity that is no greater than the random thermal vibrations and movement of the air molecules. At that point it is indistinguishable from heat and I think you can truly say it has faded to nothing. This will always happen. You can't transmit a sound in vacuum, and there will always be a gradual loss of intensity as ait travels through a gas, liquid or solid.
Sound (i.e. compression waves) will travel through any gas, solid or liquid - probably plasma as well though not really my field.It's only really a vacuum that won't transmit a sound.The denser a substance the faster sound will travel, so for example it travels about 10 times faster in steel than air.
As to how different molecules in the gas affect the transmission of the sound.... that's a really good question...! I'm guesing that lighter molecules are easier to move around (i.e. accelerate/decelerate) but then you might need to reduce the tempoerature to see teh affect as otherwise they'd be moving more quickly. As I said: good question!
Sound (i.e. compression waves) will travel through any gas, solid or liquid - probably plasma as well though not really my field.It's only really a vacuum that won't transmit a sound.The denser a substance the faster sound will travel, so for example it travels about 10 times faster in steel than air.As to how different molecules in the gas affect the transmission of the sound.... that's a really good question...! I'm guesing that lighter molecules are easier to move around (i.e. accelerate/decelerate) but then you might need to reduce the tempoerature to see teh affect as otherwise they'd be moving more quickly. As I said: good question!