The Electromagnetic Spectrum … Science@NASA: EMS (Episode 1) – An Introduction To The Electromagnetic Spectrum

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Measuring the electromagnetic spectrum

You actually know more about it than you may think! The electromagnetic (EM) spectrum is just a name that scientists give a bunch of types of radiation when they want to talk about them as a group. Radiation is energy that travels and spreads out as it goes– visible light that comes from a lamp in your house and radio waves that come from a radio station are two types of electromagnetic radiation.

Other examples of EM radiation are microwaves, infrared and ultraviolet light, X-rays and gamma-rays. Hotter, more energetic objects and events create higher energy radiation than cool objects. Only extremely hot objects or particles moving at very high velocities can create high-energy radiation like X-rays and gamma-rays.

The different types of radiation in the EM spectrum, in order from lowest energy to highest:

Radio: Yes, this is the same kind of energy that radio stations emit into the air for your boom box to capture and turn into your favorite Mozart, Madonna, or Justin Timberlake tunes. But radio waves are also emitted by other things … such as stars and gases in space. You may not be able to dance to what these objects emit, but you can use it to learn what they are made of.

Microwaves: They will cook your popcorn in just a few minutes! Microwaves in space are used by astronomers to learn about the structure of nearby galaxies, and our own Milky Way!

Infrared: Our skin emits infrared light, which is why we can be seen in the dark by someone using night vision goggles. In space, IR light maps the dust between stars.

Visible: Yes, this is the part that our eyes see. Visible radiation is emitted by everything from fireflies to light bulbs to stars … also by fast-moving particles hitting other particles.

Ultraviolet: We know that the Sun is a source of ultraviolet (or UV) radiation, because it is the UV rays that cause our skin to burn! Stars and other “hot” objects in space emit UV radiation.

X-rays: Your doctor uses them to look at your bones and your dentist to look at your teeth. Hot gases in the Universe also emit X-rays .

Gamma-rays: Radioactive materials (some natural and others made by man in things like nuclear power plants) can emit gamma-rays. Big particle accelerators that scientists use to help them understand what matter is made of can sometimes generate gamma-rays. But the biggest gamma-ray generator of all is the Universe! It makes gamma radiation in all kinds of ways.



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  1. Why do electromagnetic waves travel up and down, why don't they travel straight? This is something I've been wondering about for a while and I've look around a lot online without getting a good answer.

  2. I'm curious why the video described the length of a wave in the visible spectrum in terms of its physical length (nano meters), and not in terms of hertz. I understand light waves to be in the range of terahertz. Wif networks operate in the gigahertz range and radio waves are in the megahertz range.

  3. The representations used are quite misleading – particularly where they show continuous visible light waves emanating from TVs and various surfaces.
    While there are processes and devices that can produce light as a continuous wave (lasers and antennas, for instance), our visual world is dominated by sources that produce light sporadically and in a lumpy sort of way.

    The representation chosen is especially misleading where it concerns the absorption of light by individual molecules – a phenomenon not explainable within a classical wave description of light.

    Light exhibits wave properties, but these aren't touched on in the video other than to use wavelength as simply a number to distinguish one colour from the next. The 'continuous waves' picture is then adhered to without regard for the nature of things – building a description of reality not in keeping with observation or scientific understanding.

    The depiction of light as one-dimensional wavy things emanating in straight lines also defies a classical description of EM radiation. Of course it's difficult to show the 3D wave surfaces of true waves, but this isn't a reason to present a view so lacking in accuracy.

    Despite these issues with the concepts and their representation, the video presents a decent glimpse into the fascinating colour-dependence of light's interaction with matter!

  4. now I have the itches knowing there are trillions of invisible waves from countless sources going through my body constantly. especially my genitals which I already subject to high frequencies throughout the day. and night.

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