Energy of waves

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Offline hamza

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Energy of waves
« on: 16/10/2007 14:43:52 »
When light falls on any coloured object, some wavelengths are absorbed. I want to know , what happens to the energy asscociated with those wavelengths. Is it dissipated or is it absorbed too? If absorbed than does it bring the object to a higher energy level??


Offline JP

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Energy of waves
« Reply #1 on: 16/10/2007 15:43:05 »
Since energy satisfied a conservation law, it can't be created or destroyed in this process: all the energy hitting the object has to be put somewhere.  Where it gets put depends on the object.  In most cases, it's probably being absorbed by the object and converted to heat.  This is why objects heat up when you put them in the sun for long enough.  However, depending on the object, it could be converted to other forms of energy.  It would be common for the light to be absorbed, then re-radiated at a different wavelength, (such as infrared radiation.)  If the object absorbs more energy than it re-emits, it's going to gain energy.  (I would be careful using the term "higher energy level," however, since this usually refers to quantum objects, which can only have certain discrete energy levels.)



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Energy of waves
« Reply #2 on: 16/10/2007 17:11:15 »
An 'object' assumes liquid or solid so it will be in a 'condensed state' and, as such, will have a continuum of possible energy states available. It can, therefore, absorb photons of any frequency / energy.
If you send photons of the right frequency through a gas, they may pass right through without being absorbed. Where there are suitable energy level changes possible, then you get absorption e.g. visible light goes through the atmosphere with little absorption but infra red gets absorbed.