The Electromagnetic Spectrum <>

Electromagnetic Waves Waves that are able to travel without a medium They consist of changing electric and magnetic fields in space Often called electromagnetic radiation And also called light in general All 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 Waves Microwaves Infrared Waves (Rays) not “in-Fred” Visible Light Ultraviolet Waves (Rays) No “N” in this word! X-Rays Gamma Rays

Frequency and Wavelength The electromagnetic spectrum is divided according to the frequency and wavelength of the waves Remember … 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 meters Mainly used for communication: AM, FM signals for radio, TV

Radio Waves You 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 antenna AM= amplitude modulated, FM = frequency modulated AM=kilohertz, FM=megahertz

Radio Waves VHF= Very High Frequency…FM radio broadcasts UHF= Ultra High Frequency…FM TV broadcasts AM has been used to carry the picture signal from the TV broadcaster, FM the sound

Microwaves Also known as high frequency radio waves Freq is higher than radio, energy is higher, wavelength shorter Used for communication and cooking food

Microwaves Cooks or heats food by emitting a wave that matches the vibrations of H 2 O molecules. The constructive interference or resonance creates greater vibrations and the energy is transferred as heat.

Infrared Waves (Rays) Includes Thermal Radiation Humans can sense this with temperature sensors in the skin Thermography 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 light Pit Vipers use this sense to locate prey, they are sensitive within 0.5 degrees of temp difference Mosquitos also use this to locate prey….ouch!

Visible Light Freq. Still increasing, Amp. Still increasing, getting smaller and smaller This is the only part of the spectrum that we can SEE White light is divided into the various elementary colors by

Visible Light The elementary colors in order of decreasing and increasing freq. Red Orange Yellow Green Blue Indigo* 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 body The 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 shorter Humans 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 light It is emitted by the sun, it causes paint and plastics to break down It 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 higher Used 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, N X-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 energy They can go right through the human body and require several feet of metal or concrete to stop Emitted by radioactive decay

Gamma Rays Can cause the DNA to rearrange These mutations can be good or bad but are often bad Used in medicine to fight cancer or to kill the fast multiplying cancer cells Also used to sterilize insects for biological control Can 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 rays Humans can sense: Infrared as heat, and Visible light with our eyes