Electromagnetic Spectrum

• The complete spectrum of all forms of "light" is known as the electromagnetic spectrum.
• The electromagnetic spectrum consists of waves of lowest frequencies to highest frequencies.
• Electromagnetic waves consist of electric and magnetic fields which vibrate, making waves.
• Types of electromagnetic waves are defined by the amount of energy carried by/possessed by the photons, which are bundles of wave energy.
• The energy of a photon is represented by the formula E = hf, where h is the Planck’s Constant and f is the frequency of the EM wave.
• Gamma rays have high energies while radio waves have low energies.
• Properties of electromagnetic waves include speed (v), frequency (f), and wavelength (λ).
• Wavelength and frequency have an indirect relationship, as wavelength increases, frequency decreases.
• Frequency describes the number of waves that pass a fixed point in unit time.
• The number of cycles or vibrations undergone during one unit of time by a body in periodic motion is measured in the hertz unit.
• The hertz measurement, abbreviated Hz, is the number of waves that pass by per second.
• Wavelength is the distance between corresponding points of two consecutive waves.
• Corresponding point is two points or particles in the same phase.
• Electromagnetic waves characteristics include short wavelengths have high frequency, long wavelengths have low frequency, high frequency waves have high energy, and low frequency waves have low energy.
• Radio waves are low energy waves with longest wavelengths, including FM (frequency modulation), AM (amplitude modulation), radar, and TV waves.
• Radio waves are produced by making electrons vibrate in an antenna and are used to transmit sound and picture information over long distances.
• Low frequency waves are suitable for communication over great distances because of the curvature of the Earth, limiting its travel within 80 km, thus a repeater is used.
• Modulation is a process wherein the carrier wave is changed or varied with the loudness and pitch of the original sound, with two ways: AM and FM.
• Ground wave may follow an almost straight line path from transmitter to receiver, can hit the ground and by reflected or it can move along the earth’s atmosphere.
• Sky wave is directed upward, enters the ionosphere and is reflected back to Earth.
• Low Frequencies are used in radio navigation, government and marine radiotelegraphy, 30 to 300 kHz.
• Intermediate Frequencies are used in shortwave broadcasting, amateur communication, long-range telegraphy, 300 to 3 000 kHz.
• High Frequencies are used in shortwave broadcasting, amateur communication, long-range telegraphy, 3 000 to 30 000 kHz.
• Very High and Ultra-High Frequencies are used for FM and TV broadcasting, aircraft, police and industrial communication, radar, and radio astronomy, 30 000 kHz to 100 000 MHz.
• The ionosphere contains free electrons which absorb a portion of the energy of the passing wave, causing the electron to vibrate at a frequency that is dependent on the frequency of the electromagnetic wave.
• Satellites use radio waves to carry information from one side of the earth to another even from outer space to earth.
• Comsat is used for communication.
• Visible light is the portion of the electromagnetic spectrum that human eyes can detect and includes ROYGBIV (red, orange, yellow, green, blue, indigo, violet).
• Some night-vision goggles use IR.
• Some autofocus cameras have transmitter that sends out infrared pulses.
• Landsat is used for Earth-resource satellites.
• Radar, also known as radio detection and ranging, uses microwaves with short wavelengths and is reflected by small objects.
• Navsat is used for navigation.
• Microwaves can penetrate the atmosphere of the earth, thus it can be used for satellite communications.
• Microwave ovens use microwaves to cook food by agitating the water molecules within the food, creating molecular friction which then produces heat that cooks it.
• Ultraviolet radiation is higher energy than light waves and have shorter wavelengths than the visible light.
• Microwaves are used in terrestrial communication to transmit television news coverage from mobile broadcast vehicles back to the station.
• Microwaves have shorter wavelengths than radio waves and are used in satellite communications, radar, television transmission and cooking.
• A cell phone is a radio transmitter and receiver that uses microwaves.
• Infrared scanners are used to show the temperature variation of the body and for medical diagnosis.