Microwave ovens work almost like magic, they cook your food without any external heat and with good uniformity compared to conventional methods. But how are they able to do it? and despite their advantages, some are worried about health hazards due to electromagnetic radiation.
Will the microwaves cause you any harm? we will find answers to all these questions in this blog. So, let’s get into it.
How does it generate microwaves?
It may amaze you to learn that the invention of the microwave oven was accidental the scientist Percy Spencer was performing experiments on a device called a magnetron. Magnetrons generate powerful microwave radiation. He observed during the experiment, that the candy bar in his pocket was completely melted. That’s when it occurred to him to explore the applications of microwaves in cooking food.
From this experiment, it was observed that a high-powered traveling microwave has the capability of heating food. But of course, this raises the question of what was in the microwave that melted the candy bar?
Microwaves are electromagnetic waves in a particular spectrum like any other electromagnetic wave. They have oscillating electric and magnetic fields. If you track the amplitude of the wave in a specific area you can observe this oscillation.
In the chocolate melting accident case, the oscillating electric field component of the electromagnetic wave is responsible for cooking the food.
How Microwaves Cooks Food?
Now let’s see how these oscillating electric fields cook food. Most of the food that we consume has water in it and water is a polar molecule. The hydrogen atoms of the water molecule are placed at an angle of 104 degrees from each other. Both the hydrogen and oxygen atoms have charges. This makes the water molecule behave like a dipole. When an electric field is applied, torque is produced and the water molecule starts to rotate.
Since in electromagnetic waves, the electric field oscillates continually the water molecules will keep on oscillating, due to this oscillating rotation the molecules rub against each other and produce friction and heat in the food.
How Heat Generation Concept Transformed into Workable Product?
Now let’s look at how to convert this heat generation concept into a workable product to use the energy of the electromagnetic waves efficiently. It must be reuse several times. An efficient way of achieving this is to reflect it and keep it confined in a particular area. The best way of making this reflector is with the help of metal.
The metallic surface causes the microwave to reflect from its surface and if you keep one more reflector at the source side the reflection will keep on continuing. This way it will be able to trap the energy of electromagnetic radiation within a volume.
Understand the Concept of Resonance Cavity
However, the most efficient way of trapping electromagnetic wave energy is by the use of a technique called resonance cavity. This method also increases the intensity of electromagnetic waves.
Let’s understand the concept of resonance cavity using a simplified approach of standing waves. A standing wave is a stationary wave that fluctuates in time but does not propagate in space. When two waves superimposed on each other when same amplitude and the same frequency waves moves in opposite directions. This leads to getting an even bigger sinusoidal wave as the output.
By comparing the results of these three instances it is clear that the resultant electromagnetic wave just oscillates in its position without traveling.
Let’s examine how to produce two oppositely traveling waves practically we will get a clear solution. For this, if we understand how electromagnetic waves get reflected on a metal surface. We know that when a wave meets a reflector it returns to its source and the source will reflect the same way again to produce a third wave. This process will repeat again and again.
However, if you keep the second reflector at the intersection point of the first and second waves. The third wave produced after the reflection will be the same as the first wave this is a clever arrangement.
When you arrange the second reflector this way only two waves travel in opposite directions instead of many reflected waves and chaos. If you find out the resultant of them it will be a standing wave. When the distance between the source and reflector is an integer gets multiple of half-wavelength, standing waves get produce. Thus the wavelength of these waves determines the dimensions of the closed structure.
Now to observe a fun fact just try to measure the cavity length of the microwave oven while cleaning the oven from inside, it will be an integer multiple of this wavelength. It is clear from that; some points of the standing wave are at high energy intensity and some other points are at zero intensity.
Due to this, there would be many spots in a microwave some cold and others hot. Using cheese, you can demonstrate these cold and hot spots of your kitchen’s microwave oven. Just keep the shredded cheese inside your microwave oven for one minute. What you see after one minute is the cheese surface with a few hot spots. The presence of such hot spots causes a microwave to cook food unevenly.
In short, the cavity resonance technique we use to trap the microwaves more efficiently has led to the creation of cold and hot spots. To overcome this problem nowadays a microwave consists of a rotating plate which helps the food cook evenly without worrying about microwave safety measures.
Conclusion
The component called magnetron is responsible for producing microwaves. A magnetron emits microwaves in all directions to confine the wave to propagate in one dimension. The magnetron is attached to the waveguide. From the waveguide, the waves come into the cooking chamber.
The metal cooking chamber reflects the microwave in opposite direction called a resonance cavity which eventually heats the food.
I hope this article has cleared all your queries about how your kitchen microwave works and cooks your food evenly.