I would like to ask if light can increase an object temperature while the heat travel by radiation is neglected. Based on principal of conservation of energy, we know that energy cannot be destroyed, but it is converted from one form/type to another. So my question is, if light hits us is the light energy converted to kinetic energy of particles in the absorber that will increase the frictional force thus also contributing to the increase in temperature, or do we only receive heat by radiation only?


closed as unclear what you're asking by Emilio Pisanty, Jon Custer, Yashas, sammy gerbil, Rory Alsop Dec 10 '17 at 23:06

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  • $\begingroup$ Your question is drawing a distinction between "heat travel by radiation" which is somehow different than "light energy is converted to kinetic energy of particle." Could you please write a comment (or edit your question) to explain what the difference is? Would it help you, for example, to have a better perspective on what thermal energy is in the first place? (It only sort-of has anything to do with the "frictional force"; thermal energy is routinely exchanged without friction, as when you touch a hot stove and it burns you.) $\endgroup$ – CR Drost Dec 3 '17 at 15:58
  • $\begingroup$ Why do you think that absorption of light is different from "receiving heat by radiation"? Light is a form of electromagnetic radiation. Infrared radiation, nominally called "heat", is electromagnetic radiation. The only difference is the frequency and the resulting absorption coefficients. $\endgroup$ – Bill N Dec 6 '17 at 22:07
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    $\begingroup$ Possible duplicate of Does visible light heat things up? $\endgroup$ – sammy gerbil Dec 7 '17 at 12:57

can light increase an object temperature?

Have you ever sat in the sun, or touched an obect which was in the sunlight for a while? Yes visible light ,a part of the electromagnetic spectrum increases the temperature of matter on which it shines, depending on the atomic composition.

Please read this answer of mine as far as the difference between heat and temperature and the connection with kinetic energy.

Light is electromagnetic radiation and carries energy, riding on photons (elementary particles) that have energy= h *nu where nu is the frequency and h the planck constant.

When light hits matter, it can be reflected, absorbed, raising the kinetic energy of the material, or for appropriate frequencies raise the energy levels of the lattice or the atoms. All these interactions end up in raising the temperature of the matter under study.

So I would like to ask if light hits us does the light energy is coverted to kinetic energy of particle

depending on the frequency it can be kinetic energy, or vibrational or rotational in a lattice, raising the temperature.

will increase the frictional force thus also contribute in the increase in temperature

There is no frictional force at the level of atoms and molecules and lattices, just transfer of kinetic energy or rotational or vibrational of the molecules building up the temperature.

or we only receive heat by radiation only?

As the photons on which the classical wave rides hit matter they transfer their energy in the methods above. Heat transfer in general can happen by thermodynamic processes, like convection and contact, the bottom line is that always electromagnetic radiation, photons, are the agent by which energy is transferred between masses.

Visible light and infrared transfer the energy of the photons to the atoms, molecules and lattices , so the matter under study is heated, raising its temperature, by the radiation


... light can increase an object temperature, ...

This is right as long as the temperature of the object is not higher a levels on which the object and the radiation are in equilibration. The object will be in equilibration with it’s temperature because it is not only exposured by the radiation but radiates itself.

... while the heat travel by radiation is neglected.

What do you mean seems to be the process of convection.

Based on principal of conversation of energy, we know that energy cannot be destroy and it is converted into something else.

There are a lot of phenomenons when light hits an object. Absorption an re-emission of photons from the subatomic particles. The wavelength of the emitted light is longer on average and the difference in the wavelengths overgoes to the subatomic particles as kinetic energy. Partially the subatomic particles began to vibrate faster, partially the momentum from the photons pushes the object backwards.

... or we only receive heat by radiation only?

We receive energy from a hotter object by electromagnetic radiation in any case, would be a vacuum between as and the source (for example from the sun) or not. We receive energy from a hotter object by convection if there is some material between us and the source and the material is able to transfer the energy. For example being under a fire or far away from a fire the heated gas around the fire hardly would reach us.


Yes. The Earth is heated by the Sun's light, for instance.


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