Science em spectrum

• The electromagnetic spectrum is the complete spectrum (or continuum) of all forms of “light”.
• An electromagnetic wave consists of electric and magnetic fields that vibrate, making waves.
• The electromagnetic spectrum is a gradual progression from the waves of the lowest frequencies to the waves of the highest frequencies.
• The different types of electromagnetic waves are defined by the amount of energy carried by/possessed by the photons (bundles of wave energy).
• The energy of a photon is given by the equation: E = hf, where h is the Planck’s Constant (6.63 x 10-34 J/s) and f is the frequency of the EM wave.
• The gamma rays have photons of high energies while radio waves have photons with the lowest energies.
• The electromagnetic spectrum consists of radio waves, microwaves, infrared, visible light, ultraviolet, x-ray, and Gamma ray.
• Properties of electromagnetic waves include speed, frequency, and wavelength.
• Speed (v), frequency (f), and wavelength (l) are related in the formula: v = f x l.
• All light waves travel at a speed of 3 x 108 m/s in a vacuum.
• All parts of the electromagnetic spectrum travel at the same speed.
• Therefore, wavelength and frequency have an indirect relationship.
• In other words, as wavelength increases, frequency decreases.
• Frequency describes the number of waves that pass a fixed place in a given amount of time.
• Frequency is the number of waves that pass a fixed point in unit time; also, the number of cycles or vibrations undergone during one unit of time by a body in periodic motion.
• Usually, frequency is measured in the hertz unit, named in honor of the 19th-century German physicist Heinrich Rudolf Hertz.
• The hertz measurement, abbreviated Hz, is the number of waves that pass by per second.
• For example, a violin string's "A" note vibrates at about 440 Hz (440 vibrations per second).
• Wavelength is the distance between corresponding points of two consecutive waves.
• “Corresponding points” refers to two points or particles in the same phase.
• Electromagnetic wave characteristics: short wavelengths have a high frequency, and long wavelengths have a low frequency.
• Electromagnetic waves & Energy: high-frequency waves have high energy, low frequency waves have low energy.
• Radio waves are low-energy waves with the longest wavelengths.
• Radio waves include FM (frequency modulation), AM (amplitude modulation), radar (a system that uses radio waves to find the position of objects that cannot be seen), and TV waves.
• Radio waves are Wavelengths of 1 m (10 -1 m) and longer.
• Radio wave has Low frequency .
• Radio wave is used in many devices such as remote control items, cell phones, wireless devices, etc.
• Radio waves are produced by making electrons vibrate in an antenna.
• Radio waves 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, it limits its travel within 80 km.
• Thus, a repeater is used.
• The repeater receives the signal and retransmits it to the receiving station.
• The ionosphere contains free electrons that 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.
• Gamma Rays have the highest energy, are the shortest in wavelength, are emitted by stars and some radioactive substances, are blocked from Earth’s surface by atmosphere and thick concrete and Pb, and are used to treat cancer through radiotherapy and also for sterilization of drinking water.
• The vibrating electron radiates the energy it originally absorbed, acting like a miniature antenna, absorbing and re-radiating energy.
• Satellites for communication can carry information from one side of the earth to another even from outer space to earth.
• Satellites gather information and carry electronic equipment that transmit or receive messages carried by electromagnetic waves.
• Microwaves have shorter wavelengths than radio waves and are used in satellite communications, radar, television transmission and cooking.
• Microwaves can penetrate the atmosphere of the earth, thus it can be used for satellite communications.