# Materials and Eletromagnetic Waves

• tbfranks
In summary, microwaves cause molecules in food to polarize and vibrate, giving rise to displacement currents that emit secondary electromagnetic waves. The relaxation time for these polarized molecules is fast, so the secondary waves would cease once the microwave source is turned off. It is not accurate to say that we are eating electromagnetic waves as the waves are only present while the microwave is on. There are various models, such as Debye relaxation, that explain the time-dependent permittivity of a medium in response to a time varying signal. It is not a lie that microwaves cause polarized molecules to vibrate, but the effects are only temporary and do not persist once the microwave source is turned off.

#### tbfranks

Hello everybody!

I have an question, that seems silly, but i really need know that.

When a material is subject to waves, he starts to oscillate in the frequency of the wave and this material becomes a source of secondary waves, this justifies including the reflection process of the waves, ok?

finaly my question: when we are warming the food in the microwave we are putting the food to vibrate at a frequency of microwave. This food would be a source of secondary waves?

Are we eating eletromagnetic waves?
How i can prove if is a lie?

thanks,
[]'s

The currents that excite the secondary waves only exist due to the incident electromagnetic waves. As soon as you cease inpinging the material with an incident field, the material will cease emitting the corresponding secondary waves.

ok,

but when the waves are focusing on the material, it is nothing to vibrate? oscillation must permenacer awhile before the damping is not it? Where does this energy?

thanks

I do not understand your statement here.

When microwaves inpinge upon a food item, the incident electric fields cause molecules in the food to polarize into weak dipole moments. These dipole moments align with the incident electric field. Since the field is oscillating, the dipole moments oscillate too, causing the molecule to rotate and thus vibrate. The movement of these dipole moments gives rise to what is called a displacement current (as opposed to conduction currents which are conduction electrons moving in response to the fields). This displacement current gives rise to the secondary fields.

It is true that there is a relaxation time for the molecules when we turn off the field. A more technical explanation can be found by looking into Debye relaxation. Debye relaxation, amongst many other models like Cole-Cole, is a way of estimating the time-dependent permittivity of a medium in response to a time varying signal. So if we turn on a source and polarize the material and then turn it off, the polarization of the material will persist and slowly go away. Of course there are many complicated methods that this can happen and the Debye relaxation is probably one of the simplest.

However, needless to say, these relaxation times are very fast. I do not recall offhand what the relaxation time of water is even though I just saw a presentation on this the other week. But it is rather quick and the momentary displacement currents that arise as the polarized molecules resettle would die out very quickly after you turn off the microwave source.

Hello,

Thank you for your question. It is not a silly question at all, and I'm happy to provide an answer for you.

First, let's discuss materials and electromagnetic waves. When a material is subject to waves, it can indeed start to oscillate in the frequency of the wave. This is known as resonance, and it can occur in various materials such as strings, membranes, and even atoms. This resonance can also lead to the production of secondary waves, such as reflection or diffraction of the original wave. So, you are correct in thinking that the reflection process of waves is due to the material's ability to oscillate in response to the wave.

Now, onto your question about microwaves and food. Yes, when we heat food in the microwave, the food is exposed to microwaves which cause the water molecules in the food to vibrate at a high frequency. This vibration leads to the generation of heat, which warms up the food. However, the food is not a source of secondary waves in this case. The microwaves themselves are not reflected or diffracted by the food, so there are no secondary waves being produced.

As for your question about eating electromagnetic waves, the answer is yes and no. We are exposed to electromagnetic waves every day, from visible light to radio waves to X-rays. These waves are all around us, and we do interact with them in various ways. However, when we eat food that has been heated in the microwave, we are not directly consuming electromagnetic waves. The waves are used to heat the food, but they do not remain in the food itself. So, we are not technically eating electromagnetic waves in this case.

If you would like to prove whether or not this is a lie, you can conduct a simple experiment. Place a piece of food in the microwave and heat it for a short amount of time. Then, use a device such as a microwave detector to measure the amount of electromagnetic radiation in the food. You will find that there is no significant amount of radiation present, as it is quickly dissipated during the heating process.

Best regards,

## 1. What are materials and electromagnetic waves?

Materials are substances that have properties such as conductivity, reflectivity, and refractivity. Electromagnetic waves are a form of energy that can travel through a vacuum and do not require a medium.

## 2. How do materials interact with electromagnetic waves?

Materials can interact with electromagnetic waves in various ways depending on their properties. Some materials can absorb, reflect, or transmit electromagnetic waves. This interaction is what allows us to see, hear, and communicate using technology.

## 3. What are some common materials used in electromagnetic wave technology?

Some common materials used in electromagnetic wave technology include metals, semiconductors, and dielectrics. These materials are used in devices such as antennas, transistors, and optical fibers.

## 4. How can materials be manipulated to control electromagnetic waves?

Materials can be manipulated by changing their physical, chemical, or structural properties. For example, by altering the composition or structure of a material, we can change its ability to interact with electromagnetic waves and control their behavior.

## 5. What is the relationship between materials and the electromagnetic spectrum?

Materials and the electromagnetic spectrum are closely related as different materials have different properties and interact with different wavelengths of electromagnetic waves. This allows scientists to use materials to manipulate and control the behavior of electromagnetic waves within the spectrum for various applications.