Heat from radiation, why high v doesn't heat stuff?

In summary, lower frequency radiation such as infrared contributes more to heating up an object because it has more energy compared to higher frequency radiation like visible light. This is why objects in a microwave or under the sun get hotter even though visible light is not what causes them to heat up. This is also why materials like glass and water, which are transparent to visible light, can still absorb and block infrared radiation. Even a high intensity light like a 1kw flashlight that emits only visible light can be just as effective as a 1kw heater that emits only infrared radiation.
  • #1
DeepSeeded
113
1
Why does lower frequency radiation, like infrared, contribute to heating up an object so much more than the higher frequency radiation, like visible light?

The higher frequency radiation has more energy.

If you shine a light on something it doesn't get noticeably hotter, but if you put it in the microwave...

Same with the sun, the visible light is not what causes objects to heat up so much, yet it transfers more energy per unit time.
 
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  • #2
Glass and water are optically 'transparent' but absorb (or block) in the infrared. That's why cars get hot inside in the sun.

If you shine an intense light at your hand, I believe you will feel the heat. Remember micrwaves are about 1 kW, but flashlights are a few watts and lightbulbs are one the order of 60 to 150 watts.
 
  • #3
So if I had a 1kw flashlight that radiated only visible light it would be just as good a heater as a 1kw heater that radiated only infrared?
 
  • #4
Yes.
 

FAQ: Heat from radiation, why high v doesn't heat stuff?

1. What is heat from radiation?

Heat from radiation is a form of heat transfer that occurs when electromagnetic waves, such as infrared radiation, are absorbed by an object. This causes the object's particles to vibrate and increase in temperature, resulting in a transfer of thermal energy.

2. How is heat from radiation different from other forms of heat transfer?

Unlike conduction and convection, which require physical contact or movement of particles, heat from radiation can occur without direct contact between objects. It is also not affected by the medium through which it travels, making it possible to transfer heat through a vacuum.

3. Why doesn't high velocity (v) radiation heat objects?

High velocity radiation, or high frequency electromagnetic waves, such as X-rays and gamma rays, have shorter wavelengths and higher energy than lower frequency radiation. While these waves can still transfer heat to an object upon contact, they do so at a much faster rate and are more likely to pass through the object without being absorbed.

4. Can objects emit heat through radiation?

Yes, all objects with a temperature above absolute zero emit electromagnetic radiation. This is known as thermal radiation and is the reason why objects can be seen in the dark using infrared cameras.

5. Is heat from radiation harmful?

High frequency radiation, such as X-rays and gamma rays, can be harmful to living organisms as they have enough energy to break bonds in molecules and ionize atoms. However, most low frequency radiation, such as infrared and visible light, is not harmful and is necessary for life on Earth.

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