Why does light always have (even minimal) heat involved?

Question

I'm wondering why if there's light, there's heat.
What's making light hot?
For example: The sun gives off light and it is hot.

Answer 1

You're talking about blackbody radiation. As an object heats up, it begins radiating heat out in the form of photons (light waves). The hotter the object gets, the higher frequency the light waves it emits are (this is because the frequency of a photon is correlate to its energy level). All blackbody radiation emits photons at all energy levels (up to a certain level, which is determined by how hot the object is). The peak level, meaning the frequency that most of the photons are emitted at, is also determined by that object's temperature (and the shape of the graph is always a skewed bell curve). Anyway it just so happens that the sun's peak energy level is that of visible light.

So it's kind of the other way around from what you said: Where there's heat, there's light. But there's only visible light if the object is hot enough. Otherwise the light emitted will be at the infrared or microwave level. And if the object gets really hot, it will emit x-rays or even gamma rays.

However that only applies to blackbody radiation. There are other ways to create light, for example bioluminescence and flourescence, in which some other type of energy other than heat is transformed directly into electromagnetic radiation (light energy), so it doesn't have to get hot to give off light.

Answer 2

Light is one mechanism for moving energy from one place to another in the form of electromagnetic radiation. Heat is energy in the form of the kinetic energy of particles. When light travels through a vacuum, there are no particles, so there is no heat. When a photon (the quantum of light) hits a particle, it is either reflected or absorbed. If it is absorbed by raising an electron to a higher energy orbit, then that electron will later drop back to its original orbit, emitting another photon. If it is absorbed by increasing the kinetic energy of that particle, it has increased its heat.

When you see someone in sunlight, you are seeing the reflected/refracted photons. When you stand in the sunlight, you feel warmed because of the photons you are absorbing.

In the sun, when two hydrogen nuclei fuse to form one helium nucleus, some of their mass is converted to energy in the form of photons. Some of those photons are absorbed by other nuclei within the sun. That's what heats the sun. The photons not absorbed leave the sun and travels without loss through the universe until it is absorbed by something.

Answer 3

Light is created when electrons in atoms jump down to a lower energy level in the atom. energy is given off in the form of photons of light. Some photons are of the wavelength seen by the eye, but others are of a slightly smaller or larger wavelength - for example ultra-violet and infra-red.

Infra-red light warms things up when it hits them, because the wavelength is the right length to wobble atoms. Heat is a measure of how much movement atoms are making.

As far as I know, glow sticks do not creat heat, so there are some light sources which are not hot.

Answer 4

Because light is usually the result of an energetic reaction that also gives off heat.

The Sun: Ball of burning gas, resulting in light and heat.

Light bulbs: Thin filament that glows due to electrical current, resulting in light and heat.

I'm not very familiar with the physics of chemical lighting, but i'd guess that there may be a small amount of heat energy released, as well as luminescence, as a result of the chemical reaction.

Answer 5

Even very efficient light sources eg fluorescent and LED are not 100% efficient .
The inefficiency ie the losses is the heat produced
A perfect light source would be 100% efficient and thus produce no heat but we don't live in a perfect world, there are always losses, heat is like friction

Answer 6

The heat from the sun varies with distance and other factors. Light containes energy that is transfered in the form of heat... Energy is always being converted form one form to another.

Answer 7

Energy is needed to replace not only the mechanical energy of our bodily exertions, but also the heat we continually give off to the environment. And that we give off heat is not accidental, but essential. For this is precisely the manner in which we dispose of the surplus entropy we continually produce in our physical life process.

This seems to suggest that the higher temperature of the warm-blooded animal includes the advantage of enabling it to get rid of its entropy at a quicker rate, so that it can afford a more intense life process. I am not sure how much truth there is in this argument .
Just maybe this could be placed into out Sun's example of being

Answer 8

Because power is needed to create that light and when power is expended, heat is created. In electricity, P=I*R or Power is equal to the current passing through the device times the resistance to that flow. Even LED's consume power although it's minimal.

When you have a campfire, the consumable is wood..... more light and heat.

Good question.

Answer 9

Because the energy needed to create light give off heat.

Answer 10

Any body that is above Absolute Zero in temperature radiates.
Radiation is essentially the result of charged particles moving.
Since Absolute Zero is the temperature where atomic motion would stop that is why at 0 there is no radiation and above zero there is.

So ANY form of radiation also comes with heat because heat is what gives the energy to move.