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/sci/ - Science & Math

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3372462 No.3372462 [Reply] [Original]

Dear physicists, how can light burns? I don't understand this. Explain?

>> No.3372470

Light is energy.

>> No.3372475

>>3372470
yes, but so is wind. that doesn't explain it

>> No.3372479

>>3372475
dem jiggling atoms

>> No.3372482

http://www.time.com/time/magazine/article/0,9171,908175,00.html?promoid=googlep

>> No.3372483

>>3372475
concentrated light burns.

Areas receiving more light receive more energy that gets converted to heat. An area that has 200* the amount of light it would receive naturally gets 200* the energy.

>> No.3372486

>>3372462
http://en.wikipedia.org/wiki/Heat_transfer#Radiation

>> No.3372487

>>3372475
wind is energy?

>> No.3372506

>>3372462
light=electromagnetic oscillations (EM wave) = wave
atoms = nucleaus and electron shell = dampened oscillator
wave applied to oscillator increases the oscillation amplitude of electron due to resonance, as the amplitude increases dampening leakages increase and more energy is leaked into whole atom oscillation (including the heavy nucleus). Hence there's high amount of energy leaked into the motion of the whole atom = here you go that's the definition of material temperature (internal energy).
If energy losses < energy gain there's energy accumulation until losses = gain. If internal energy accumulated "high" then you perceive it as burning (by "high" you can put any threshold you wish there is no uniform consensus - but if pic. related then the temperature is the temperature needed to ignite wood or textiles).

>> No.3372514

>>3372487
varying wind intensity is energy, it's called sound. Constant flow of ideal frictionless gas is has only the kinetic energy so the only thing that'll happen is that it will slowly accelerate you - not heat up unless friction is introduced (in which case it gets clear that the energy comes from internal oscillations of wind/air atoms).

>> No.3372517

>>3372514
*actually just to correct it varuing wind intensity with average no displacement = sound

>> No.3372515
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3372515

>>3372487
RENEWABLE energy

>> No.3372520

someone please tell me (or refer to wiki article) how light can make molecules jiggle

>> No.3372521

Light hits your skin, and the energy contained in it is turned into heat. This heat causes the destruction of skin cells, leading to sun burn.

>> No.3372527

>>3372520

read this:
>>3372506

>> No.3372528
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3372528

>mfw this thread

>> No.3372530

photons moving the speed of light bump into the particles in your skin, causing them to move slightly faster. The faster moving particles are what you call "heat"

>> No.3372533

>>3372520

Light passes by a particle, and some combination of magnetism and/or gravity grabs the particle and makes it move.

>> No.3372542
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3372542

>>3372533
>>3372530

>> No.3372550

>>3372506
damn, so a bunch of coupled oscillators?
moving back 200 years, is there a more simple explanation in classical physics?

>> No.3372575

>>3372550
not really since 200 year in the past people didn't understood how it works.

But generally if you want it particle way it's something like that:

E_atom + E_photon -> (E_atom + A*E_photon - C) + (B)*E_photon + C

where
A = probability that photon will get absorbed
B = 1-A
C = loss in the form of photon or phonon (pressure wave) - let's just not care about the expression of it's energy