What is Energy absorption: Definition and 23 Discussions

Specific absorption rate (SAR) is a measure of the rate at which energy is absorbed per unit mass by a human body when exposed to a radio frequency (RF) electromagnetic field. It can also refer to absorption of other forms of energy by tissue, including ultrasound. It is defined as the power absorbed per mass of tissue and has units of watts per kilogram (W/kg).SAR is usually averaged either over the whole body, or over a small sample volume (typically 1 g or 10 g of tissue). The value cited is then the maximum level measured in the body part studied over the stated volume or mass.

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  1. H

    B Apparent missing negative phase oscillation energy - where is it?

    When an oscillator produces waves - let's say they are highly focused - that are damped by a second negative phase oscillator, where is the wave energy? The energy in each set of waves must still exist. Has it become hidden?
  2. kostasstefan

    I Energy Transfer Through Materials

    Hi and thanks for taking the time to read my question. So, if i take an element and place it on top of another element and heat it, will the heat energy pass through the first and charge the other or it'll melt both elements? Thanks!
  3. r12214001

    Energy conversion question

    Why I cannot get the right answer by using △T=(3/2)nK△T to solve problem C:
  4. M

    How to Measure Impact Force / Energy Absorption

    Hi, I am a bit out of my league here, but had a question. I have 5 pieces of .25" thick foam/padding of different densities, and I wanted to measure which one absorbs the most energy (weakens the impact) when struck by a fist/punch or even a ball, how would I do that? I ran across a...
  5. darksat

    Infrared energy absorption of H20 molecules as a percentage of energy

    I eventually managed to find that a CO2 molecule can absorb about 8% of infrared energy passing through it that's radiated from Earth but its actually been incredibly hard to find a comparable figure for H2O molecules. Has anyone got a percentage figure for H2O in the form of atmospheric water...
  6. thaiqi

    Why doesn't the atom absorb heat energy when it is low?

    (In my last thread) Mentor Dale said: " An atom in the ground state can absorb energy from the environment including thermal radiation. Once it has done so it will be excited and will no longer be in the ground state. An excited atom can radiate and go to a lower energy state, but an atom in the...
  7. HastiM

    I How to increase the energy of an electron

    Hello, in class we learned about the hydrogen atom and in particular the quantum states describing the electron in hydrogen atom (we denoted them as usual by 1s, 2s, 2p etc.). Whenever we talked about state transitions of the electron, like transition from 1s to 2p state, we imagined an...
  8. C

    Impact Energy Absorbed by a Material

    Problem I am designing a force sensing system with piezoelectric force sensors to determine the impact force on an object during a collision. The sensor will be placed between an aluminum block and either a TPU or PLA 3D printed "cover". The cover will be 5cm thick...
  9. J

    I Energy transfer during uphill vs downhill running

    Hello Physics Gurus, Please critique the following logic... When a runner hikes/runs to the top of a mountain, the chemical potential energy inside the muscles transferred into the potential energy of the runner's body mass at the higher elevation (Pe = mass*gravity*height = mgh). Energy is...
  10. X

    Find The Percent Change In K.E. Of Rod Hit By Putty

    I'm trying to solve this problem, however I'm unsure if my reasoning is correct - I do agree with the answer, but something seems wrong to me in my reasoning. 1. Homework Statement A rod is on a frictionless surface, and is defined by the length L and mass M. It is hit on one end by a piece...
  11. Chemchampa

    Heat Transfer and Air Flow

    Hello, I have here a complex question. My background is Chemistry and Optoelectronics. I wasn't the best when we were studying Thermodynamics at uni so I have some knowledge-gaps. Anyways, here is my problem. Can somebody explain me the whole process of the convection in the coffee roaster. So...
  12. NaiveTay

    I Can a Photon be Absorbed Without the Exact Energy Level?

    In my education of QM, I've heard countless times how energy is quantized by Planck's Constant, and how radiation is only emitted and absorbed in these discrete steps. Recently I've heard that that's not the full picture of energy, and I was hoping you could draw some clarity for me. In...
  13. Z

    Vaporization and Energy absorption

    In modern nanotechnologies, metals can be vapourized to coat onto the surface of another material as a thin but hard protective layer. How much energy would it take to heat 0.55 kg of iron from 1400oC to vapour at 2050oC?
  14. C

    Energy Absorption from Impact

    Hi, I am doing a drop impact testing on a football shin guard. I know how to find the impact force but how do I determine the energy absorbed by shin guard during impact?
  15. marellasunny

    Damper energy absorption during rebound is different from compression

    I understand that the purpose of a damper system is to stop the spring from bouncing during rebound. But,technically speaking,I do not understand the matter of energy absorption in the damper during rebound. 1.The damper is absorbing energy during compression along the bump and dissipating...
  16. M

    Reducing Force: Understanding Energy Absorption in Crashes

    Does reducing acceleration mean reducing force acting upon the object. And does this mean absorbing energy from the object? If so where is the energy absorbed in case of crashes where air bags inflate to reduce force?
  17. S

    Mechanism of Bond Energy Absorption

    When scientists analyze proteins (chains of amino acids), often times light spectroscopy is used. Light is passes through a cuvet containing dissolved protein, and the absorption is measured. My question is: How do bonds absorb energy? What is the actual mechanism? I have been told that the...
  18. O

    Energy absorption by aircraft fuselage

    Homework Statement 1. When an aircraft flies above the clouds during the daylight period it is continuously exposed to sunlight. This sunlight heats up the cabin. Although the outside air temperature at cruise altitude is – 56 degrees this is still one of the determining factors for the sizing...
  19. S

    Energy Absorption: How Atoms Interact with Waves

    Energy "absorption" Hi, Apologies if I've misinterpreted / mis-read something here (not a physics student - just a general interest). Just hoping to be put straight on something fairly simple: Are atoms / electrons able to interact with waves ie microwave / radio waves? If so, are there...
  20. P

    Aluminum Extrusion - Specific Energy Absorption

    Hey guys, doing some research here on Specific energy absorption of Aluminum 1016 T6 extrusion. 300mm length. I have to try and increase the SEA within this control volume. I have couple ideas, what do you think? I am going to apply a 150N load to the extrusion through compression and compare...
  21. H

    Question about energy absorption

    Ok, so I just took part in this lab for my Kinesiology class and I am having a little trouble figuring out the answers. It is my first time on this board and was just wondering if anyone could help. Here is the scenario. Energy absorption is a critical component of injury prevention, in many...
  22. Z

    Calculating Energy Absorption of 2.0kg Bag of Ice

    A 2.0 kg bag of ice is used to keep a cooler of pop cold for 5.5 h. If the ice had an initial temperature of -4ºC and, after 5h, was liquid water with a temperature of 3ºC, find the power of energy absorption. Any help would be great. I don't know where to start:confused:.
  23. C

    Can We Stack Solar Panels to Increase Solar Energy Absorption?

    Is it possible to have solar panels one over the other with little space between them to get 10 panel stacked structures to increase the amount of solar energy absorbed? There are four solar panels. Another 4 on top of them leaving some space between this four and the bottom four. In the...