Higher and Lower Frequencies

by Jared Rovny

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    00:01 Let's discuss a few of the important kinds of light that were on a spectrum.

    00:05 First, let's discuss the higher frequencies, the frequencies above the purples and violets.

    00:10 And as you might expect, we call this the ultraviolet, the above the violet spectrum.

    00:16 So these are high frequency beams.

    00:18 The ultraviolet kind of light is invisible, it's slightly higher energy than the blue light and we'll talk about the energy and how we can compare energy and frequency very soon.

    00:27 In this kind of light can cause sunburn sometimes even DNA damage and cancer as well.

    00:32 So this is the sort of light that you're getting for example from the sun if you're outside and the sun is shining on you possibly causing some dangerous effects.

    00:39 Going slightly even higher in frequency, we have x-rays.

    00:43 These are even higher energy, meaning smaller wavelengths and as we've already discussed these are useful for probing matter to see their internal structure because the size of x-rays are comparable to the size of the distance between the atoms and its structures.

    00:56 These rays can be ionizing and we talked a little bit about ionization when we mentioned anions and cations.

    01:03 Those are particles that have had electrons lost or electrons gained.

    01:07 When we ionize something that means we have hit it with the enough energy that it could lose electrons and gain a different charge.

    01:14 Ionizing radiation gains a lot of talking in the literature and in the public sphere because we talk about the kinds of radiations that can actually cause serious damage to especially to DNA.

    01:26 And ionizing radiation can certainly do that.

    01:28 Finally, going even higher in the electromagnetic spectrum to more and more energetic waves we have what are called gamma rays and this is the Greek letter gamma that we have here, it's a little loop.

    01:40 So these gamma rays are considered certainly to be a radiation.

    01:44 So gamma radiation, it's sort of a confusing terminology perhaps we call electromagnetic radiation, a name for all electromagnetic waves but sometimes and probably more often we call radiation the specific very high energy sorts of waves which can be very damaging.

    02:02 So gamma rays are one of the best examples of this.

    02:05 A very high sort of energy that can certainly be ionizing and is an example of a kind of wave that comes from the cosmic rays and most of these rays, thankfully for us, are filtered by our atmosphere and magnetosphere.

    02:17 We can also go on the other direction.

    02:20 Let's look at some of the lower and lower frequencies on the spectrum.

    02:24 These are lower energies and they're below the red.

    02:27 So instead now of ultraviolet being above the purple, we're now going to infrared or below the red part of the visible spectrum.

    02:36 These infrared rays of light are lower frequency even in red light and have as I said even lower energy.

    02:43 This kind of radiation is in fact emitted by anything that has some heat to it and so we could use for example infrared goggles to see through walls and just see the heat of these infrared rays that are usually moving through, for example, the walls.

    02:56 Going lower in our energy and this would also correspond by the way to higher wavelengths so keep that in mind, lower frequencies but higher wavelengths.

    03:06 These microwaves are useful for example for exciting water molecules.

    03:10 And this might be your most familiar exposure to the idea of a microwave.

    03:15 We use it to excite water molecules in food so be aware that by the way your microwave is always heating up the water in a food which is why substances you put in the microwave would heat up much faster depending on their water content.

    03:27 So these microwaves are still lower energy than the infrared waves, but by using many, many, many microwaves we can still arrive at heating amplitude.

    03:36 We can go one step lower and talk about radiowaves.

    03:39 Radiowaves have a very, very long wavelength which means that they have a very low frequency and they're useful for sending signals due to their long wavelengths and low, low frequencies since they don't interfere very much with the things around them.

    03:53 Again, due to those long, long wavelengths.

    About the Lecture

    The lecture Higher and Lower Frequencies by Jared Rovny is from the course Light: Electromagnetic Radiation.

    Included Quiz Questions

    1. Radiation that can detach electrons from atoms and molecules, thereby ionizing them
    2. Radiation which can be absorbed by matter
    3. Radiation which can collide with ions
    4. Radiation which is positively charged
    5. Radiation which is negatively charged
    1. Ultraviolet light
    2. Microwave
    3. Radio waves
    4. Red light
    5. Green light
    1. Radio waves, as they have very long wavelengths they rarely interact with the surrounding
    2. Gamma rays, as they can penetrate through materials easily
    3. Microwaves, as they rarely interact with matter
    4. Infrared light, similar to how with infrared goggles it is possible to see through walls, infrared light can be used to transmit signals over long distances as they rarely interact with objects
    5. Ultraviolet light, as it can penetrate miles through the atmosphere and reach our skin from the sun, it can similarly be used to send signals over long distances through the atmosphere

    Author of lecture Higher and Lower Frequencies

     Jared Rovny

    Jared Rovny

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