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How does a microwave oven work?

Discussion in 'Off-Topic' started by Jeanh, Jul 30, 2015.

  1. A Microwave oven heats your food by rapidly vibrating water molecules inside your food.
    What are microwaves anyway ?
    Electromagnetic Spectrum
    Microwaves are part of the electromagnetic spectrum. Before I lose you at this point with this jargon, electromagnetic spectrum consists of a combination of electric and magnetic waves vibrating at different frequencies aka different times per second.
    Electromagnetic spectrum consists of everything from visible light, UV which causes sun tan and eventually cancer to Radio waves which were your grandfather's only source of entertainment for a while.

    Coming to Microwaves
    Microwaves are part of the electromagnetic spectrum snuggled between Infra-Red which you can use for Night Vision and Radio waves. Although called micro, the wave length (that is crest to crest or trough to trough) distance is usually in millimetres while for visible light is usually a 10,000 times smaller than that.
    Microwaves were usually used for applications such as radar when suddenly it was discovered that they heat human food.

    The fact that they can heat food was discovered by accident.

    In 1945, while working near a magnetron (a device which produces microwaves), an engineer found that the candy bar inside his pocket was melting. Why he had a candy bar inside his pocket as a grown man was never asked.
    He tried it on corn kernels with great success (after all this is real science) and an egg which put him probably on a probation list.
    Raytheon, the huge corporation he was working for immediately commercialised the technology for household applications. The microwave over grew smaller and smaller till they are what you see now.

    So how does a microwave really work ?
    Your food quite similar to you, is mainly composed of water and therein lies the secret of the microwave.
    If you hurt your brain a little and try to remember the chemistry classes from high school, a water molecule is composed of two atoms of hydrogen and one of oxygen like the figure below.

    Water Molecule: Looking at it closely.
    However, you will notice that the hydrogen molecules seem to be grouped together on one side and the oxygen atom is hanging out alone on the top.

    What this does is create something called a dipole moment which kinda means that the molecule is polarised that is slightly positive on one side and negative on the other.

    Remember this is important as this would make it make it sensitive to any electric field specially a vibrating one.

    Now Apply a Rapidly Oscillating Electric Field, That is Microwaves
    The commercial microwave in your house operates at approximately 2.4 GHz, that means that the electric field changes polarity 2,400,000,000 times a second.
    When applied on your food, this vibrates the water molecules rapidly at a similar rate. The water molecules rub against each other and neighbouring molecules rapidly heating up and your food.

    What are microwaves harmful?
    Microwaves, unlike gamma rays or X-rays are non ionising radiation, is not harmful at all by itself. However, as you are composed of water mostly, it will burn you badly. The mesh on the door of the microwave, which makes it hard to look at the burrito you are heating up is actually there to prevent the microwaves from escaping.
    lablab likes this.
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