The Electromagnetic Spectrum . Electromagnetic Waves Waves that are able to travel without a medium...

The Electromagnetic Spectrum

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Electromagnetic Waves

Waves that are able to travel without a mediumThey consist of changing electric and magnetic fields in spaceOften called electromagnetic radiation And also called light in generalAll of these waves travel at 300,000,000 m/s or the speed of light (that is 669,000,000 mi/hr)Stars emit all of the various EM spectrum waves

The spectrum is divided into:

Radio WavesMicrowaves Infrared Waves (Rays) not “in-Fred”Visible LightUltraviolet Waves (Rays) No “N” in this word!X-RaysGamma Rays

Frequency and Wavelength

The electromagnetic spectrum is divided according to the frequency and wavelength of the wavesRemember …v = f x so

If the velocity is the same for all of the parts, then as the frequency increases, the wavelength gets shorter

Radio Waves

Lowest Freq., longest wavelength, lowest energy of the EM Spect. = 1cm to 100’s of metersMainly used for communication: AM, FM signals for radio, TV

Radio WavesYou CANNOT hear radio waves. They are flowing through the room right now. AM and FM are used for different “radio” bands. AM is used to send analog signals to TV, FM sends analog signals to TV by antennaAM= amplitude modulated, FM = frequency modulatedAM=kilohertz, FM=megahertz

Radio Waves

VHF= Very High Frequency…FM radio broadcastsUHF= Ultra High Frequency…FM TV broadcastsAM has been used to carry the picture signal from the TV broadcaster, FM the sound

Microwaves

Also known as high frequency radio wavesFreq is higher than radio, energy is higher, wavelength shorterUsed for communication and cooking food

Microwaves

Cooks or heats food by emitting a wave that matches the vibrations of H2O molecules. The constructive interference or resonance creates greater vibrations and the energy is transferred as heat.

Infrared Waves (Rays)

Includes Thermal RadiationHumans can sense this with temperature sensors in the skinThermography is a special type of photography that takes pictures of temperature differences. Used for finding tumors, finding thermal energy leaks in homes, locating criminals, “seeing” in the dark Humans also emit this energy

Infrared Waves (Rays)These have a higher frequency than microwaves, higher energy than microwaves, and a shorter wavelength…you should see the trend by now. They are called Infra (lower) red because they are found below the wavelengths of red visible lightPit Vipers use this sense to locate prey, they are sensitive within 0.5 degrees of temp differenceMosquitos also use this to locate prey….ouch!

Visible Light

Freq. Still increasing, Amp. Still increasing, getting smaller and smallerThis is the only part of the spectrum that we can SEEWhite light is divided into the various elementary colors by

Visible Light

The elementary colors in order of decreasing and increasing freq. RedOrangeYellowGreenBlueIndigo* Some do not recognize this one

Violet

Visible Light

The moon is an illuminous body in that it reflect light, it is illuminated by a luminous bodyThe sun and all stars are luminous bodies because they emit visible light

Visible Light

Night vision goggles still use visible light but they have an extremely strong ability to gather light or has a high resolution

Ultraviolet Light (UV)

There is no “N” in this word!Freq. Is still getting higher, amplitude higher, wavelength shorterHumans do not have the ability to “see” this type of radiation; Hawks, bees, and other animals CAN see UV

Ultraviolet Radiation (UV)

It is called ultra (higher) violet because it is located at a slightly higher freq. And slightly shorter than Violet lightIt is emitted by the sun, it causes paint and plastics to break downIt kills skin cells and is used in hospitals and nail salons to sterilize equipment, it also causes cataracts and vision damage

X-Rays

Freq continues to increase, is getting VERY small, and energy is getting higherUsed to see inside of living things without cutting them open. X-ray film is exposed when X-rays hit it.

X-Rays

The denser atoms absorb the x-rays while the less dense allow the x-rays to pass through and expose the film.This is why bones and teeth and metal show up on X-ray films. They are made of denser atoms. While the soft tissues are mainly C, H, O, NX-rays can cause DNA shifts in sex cells and can lead to birth defects. Normally we do not take X-rays of babies or of the reproductive cell areas of humans within their reproductive years.

Gamma Rays

These have the highest frequency, shortest wavelength and highest energyThey can go right through the human body and require several feet of metal or concrete to stopEmitted by radioactive decay

Gamma RaysCan cause the DNA to rearrangeThese mutations can be good or bad but are often badUsed in medicine to fight cancer or to kill the fast multiplying cancer cellsAlso used to sterilize insects for biological controlCan be used to kill bacteria, usually UV is used due to the lower risk

The Electromagnetic Spectrum

Parts: Radio waves, Microwaves, Infrared waves, Visible light, Ultraviolet, X-rays, Gamma raysHumans can sense: Infrared as heat, and Visible light with our eyes