The Electromagnetic Spectrum Part 2 Chapter 4 The Electromagnetic Spectrum Part 2

Radio waves Includes FM, AM, radar and TV waves Used in many devices such as remote control items, cell phones, wireless devices, etc.

Microwaves First used in radar, now used in communication (wireless LAN networks), and consumer use (microwave ovens). medical applications in cancer treatment (destroy tumors by heating them). Most radio astronomy uses microwaves “Active Denial System” – the “Pain Ray”

Microwaves The Active Denial System (ADS) is a non-lethal weapon developed by the U.S. military. It is a micro-wave transmitter used for crowd control. Informally, the weapon is also called the pain ray. The ADS works by directing microwave radiation toward the subjects. The waves excite water molecules in the epidermis to around 130 °F (55 °C), causing an intensely painful sensation of extreme heat. While not actually burning the skin, the burning sensation is similar to that of a light bulb being pressed against the skin. Wireless LAN (Local Access Network) protocols, such as Bluetooth also use microwaves.

Infrared Missile guidance systems use the emission from a target of electromagnetic radiation in the infrared part of the spectrum to track it. Infrared radiation can be used as a heating source. For example it is used in infrared saunas, and also to remove ice from the wings of aircraft (de-icing). Infrared thermomedic therapy uses thermal technology to provide compressive support and healing warmth to assist symptom control for arthritis, injury & pain. IR data transmission is also employed in short-range communication among computer peripherals and personal digital assistants (PDA’s) Weather satellites produce infrared images to aid in the prediction of weather.

Infrared Waves Infrared radiation is popularly known as "heat" Used in heat lamps, de-icing systems and thermomedic therapy. Missile guidance systems, short range communication systems Weather satellites

Can be detected with special devices such as night goggles

Weather satellites track weather systems using infrared.

Visible Light The portion of the electromagnetic spectrum that human eyes can detect ROY G BIV (red, orange, yellow, green, blue, indigo, violet) Red is the lowest frequency and violet is the highest frequency

We perceive electromagnetic energy having Visible Spectrum We perceive electromagnetic energy having wavelengths in the range 400-700 nm as visible light.

Ultraviolet Radiation To help thwart counterfeiters, sensitive documents (e.g. credit cards, driver's licenses, passports) may also include a UV watermark that can only be seen when viewed under a UV-emitting light. Some brands of pepper spray will leave an invisible chemical (UV Dye) that is not easily washed off on a pepper sprayed attacker, which would help police identify them later. Fluorescent lamps produce UV radiation by ionizing low-pressure mercury vapor. A phosphorescent coating on the inside of the tubes absorbs the UV and converts it to visible light. Some animals can see into the near ultraviolet. Many insects use the ultraviolet wavelength emissions from celestial objects as references for flight navigation. Ultraviolet traps called bug zappers are used to eliminate various small flying insects. They are attracted to the UV light, and are killed using an electric shock.

Ultraviolet Can cause skin cancer and blindness in humans Used in tanning beds and sterilizing equipment UV watermarks UV identification

Bee vision is very different from human vision, they perceive colors we are simply incapable of seeing. Most insects have light sensitive cells, or photoreceptors, that are sensitive to ultraviolet light.

X-Rays Primarily used in medicine.

X-Ray Scanners

X-Ray Diffraction The diffraction of X-rays is used to disperse X-rays in a spectrometer and to determine the structure of crystals or molecules.

Gamma radiation Gamma radiation can impart significant damage to a living cell. This property means that gamma radiation is often used to kill living organisms, in a process called irradiation. Applications of this include sterilizing medical equipment and removing decay-causing bacteria from food. Due to their tissue penetrating property, gamma rays have a wide variety of medical uses such as in CT Scans and radiation therapy. However they have the ability to cause cancer as well. Despite their cancer-causing properties, gamma rays are also used to treat some types of cancer. The procedure called gamma-knife surgery uses multiple concentrated beams of gamma rays in order to kill cancerous cells. Gamma rays are also used for diagnostic purposes in nuclear medicine to track radioisotopes that are administered to a patient. In the US, gamma ray detectors are used as part of the Container Security Initiative (CSI). The objective of this technique is to pre-screen merchant ship containers before they enter US ports.

Gamma rays Highest energy and most dangerous type of radiation. Can cause cancer through damage to DNA. Blocked from Earth’s surface by atmosphere. Used in medicine and irradiation.

Irradiation

Gamma Knife

Electromagnetic Waves

Demonstrations Light is a Wave Using Polarizers. Colored Slides. Ne and Ar spectral tubes.

Star Finder Video: Electromagnetic Spectrum

Homework Chapter 4: Worksheet 2