The Electromagnetic Spectrum X - The Gamma
Written by Translator on June 17, 2008 – 7:32 pm -Crossposted at Dailykos.com
Well, this will conclude the series. I appreciate all of the comments, and have tried to adapt this series to respond to them, including more links and pictures. Some of them are interesting, and some just help make the point. Unfortunately I was unable to embed any this time for reasons beyond my control.
Gamma EMR is from 10 picometers on down to the mathematical limit of zero (obviously never attaining the limit). Because of the extremely high energies associated with them, gamma rays are difficult to contain.
Tags: Compton scattering, Electromagnetic spectrum, Food preservation, Gamma, Medical imaging, Pair production, Photoelectric effect, Teaching
Posted in Diaries | 2 Comments »
The Electromagnetic Spectrum IX - X-Rays
Written by Translator on June 15, 2008 – 6:50 pm -Crossposted at Dailykos.com.
he end of the 19th Century and the beginning of the 20th were heady times in physics. Within a month of Wilhelm Konrad von Roentgen’s publication of the discovery of X-rays, Henri Becquerel announced the discovery of natural radiation from uranium ore. Things were beginning to move quickly.
X-rays are generally agreed to have wavelengths from 10 nanometers to 10 picometers, making them the next region higher in energy with respect to UV. Roentgen accidentally discovered X-rays while performing experiments with a “Crookes Tube”, an evacuated glass tube in which two electrodes are sealed and a high voltage direct current applied.
Tags: Bragg Equation, Electromagnetic spectrum, Father's Day, Ionizing radiation, Medical imaging, Teaching, X-Rays
Posted in Diaries | 5 Comments »
The Electromagnetic Spectrum VIII - The Ultraviolet
Written by Translator on June 12, 2008 – 6:22 pm -Crossposted at DailyKos.com.
Last time we beat the visible to death (thanks to the Rescue Rangers for listing), and are now ready to move on to the next higher energy region, the ultraviolet. It is called that because it is above (ultra) the violet in frequency, and thus has a shorter wavelength. UV is an extremely important region of the EM spectrum, for reasons good and ill.
Many authorities assign the UV to wavelengths from 400 nanometers to around 10 nm, thus bumping up against X-rays at the short end. Once again, there is no clear delineation where one starts and the other ends, but this is a pretty good rule of thumb.
Tags: Cell damage, DNA, Electromagnetic spectrum, Sterilization, Teaching, UV, UVA, UVB, UVC, Vacuum UV
Posted in Diaries | 3 Comments »
The Electromagnetic Spectrum VI - Visible Light Part 2
Written by Translator on June 9, 2008 – 9:38 pm -Crossposted at DailyKos.com.
We talked a bit about how visible light is generated and propagates last time, but this time I want to focus on the phenomenon of human vision. This a obviously a narrow sliver of a large topic, but is so significant that it should be discussed.
Vision in general is the interaction of EMR with sensitive cells in an eye. As I said about infrared, some reptiles “see” in the IR. In future, I will discuss the idea that many insects “see” in the ultraviolet.
Tags: cGMP, Cones, Electromagnetic spectrum, Rods, Teaching, Visible Light, Vision
Posted in Diaries | 1 Comment »
The Electromagnetic Spectrum IV - Shorter Lambda than Microwaves
Written by Translator on June 6, 2008 – 8:40 pm -Obviously, it is not possible to touch every item that this vast subject holds, and I depend on readers to open up more frontiers. We barely scratched the surface about microwaves, but have to move to more energetic bands.
The infrared band lies just above the microwave, and just below the visible. Issac Newton discovered it by taking a thermometer and placing it in different spots on a projection of a spectrum of sunlight provided by a simple glass prism. He noted that there were area of higher temperature below the violet (now called ultraviolet) and above the red (now called infrared). These terms come from the natural distribution of a solar spectrum by a prism, the red being at the top of the graph.
So, here once again we go. Read more »
Tags: Electromagnetic spectrum, EMS, Infrared, Teaching, Vibrations of atoms
Posted in Alternative Energy | 8 Comments »