5 LESSON_Q2

• Electromagnetic spectrum is a continuum of electromagnetic waves arranged according to frequency and wavelength
• Regions of the electromagnetic spectrum

  • Radio waves
  • Microwaves
  • Infrared
  • Visible light
  • Ultraviolet
  • X-rays
  • Gamma rays
• Electromagnetic waves


  • They are series of disturbances that transfer energy through a field and propagate without a need for matter as medium
  • They are a transverse wave
• Radiation


  The term used to describe the transfer of energy in the form of EM wave and that energy travels through space
• Electromagnetic waves are produced by the accelerating electrons from a changing magnetic field that produces an electric field and a changing electric field that produces a magnetic field
• Both electric and magnetic fields oscillate perpendicular (90°) to each other and to the direction of the propagating wave
• EM waves can travel in a medium and their speed varies according to material type but instead of disturbing the matter, EM waves disturb the space by affecting its electric and magnetic properties
• EM waves can travel in a vacuum or empty space at a constant speed of 3 x 10^8 m/s (speed of light)
• Radio waves


  • Longest wavelength but of lowest frequencies and energy, therefore deemed safe
  • Used as carrier information in radio communication and television
  • Used by astronomers to gather information about celestial objects and various parts of the universe using radio telescopes
  • Not line of sight, can pass through walls, longer range and not light sensitive
  • Disadvantages: Communication devices that make use of the same frequencies interfere with their transmission, easier to "eavesdrop" since signals are transmitted in space rather than a wire, more costly than infrared, can be a noise pollution if too much sound is produced, may break ear drums and affects heartbeat with unregulated amplitude and frequencies
• Microwaves

  • Smaller wavelengths than radio waves
  • Used in cooking, texting, RADAR, television transmission and telecommunications
  • High energy microwaves radiation at frequencies from 300 MHz to 300 GHz can be carcinogenic and cause thermal effects, increasing the temperature of exposed organisms
• Infrared


  • Refers to EM waves with frequencies below the visible red light
  • Our bodies radiate infrared, thus in night vision goggle it emits variety of colors
  • Used in camera technology, short distance transfer of files between phones, satellite photographs, scanners for temperature, used for medical diagnosis, remote controls in TV's, video cassette recorders and other electronic devices, infrared telescopes and electrical heaters
  • Near Infrared waves are short and not hot, can be used as infrared therapy, has many positive effects: detoxification, reduce muscle tension, improved circulation, relaxation boosting immune system, lowering blood pressure and lowering side effects of diabetes
  • The heating effect of IR makes them particularly dangerous to susceptible tissues, such as skin and eyes as they can cause burn, but this can be avoided because it provides a warning mechanism in the form of pain
• Visible spectrum


  • The range of electromagnetic spectrum that the eyes can detect and make us see and appreciate the beauty of our surrounding
  • It ranges from 4.3 x 10 to 7.5 x 10 hertz
  • The color with the lowest frequency is red, followed by orange, yellow, green, blue, indigo and violet
  • They travel at same speed but differ in frequency and wavelength
• Infrared waves


  Short and not hot, we cannot see them but feel them as heat
• Infrared waves


  • Heating effect makes them dangerous to susceptible tissues like skin and eyes, can cause burns, but provides a warning mechanism in the form of pain
  • Can be used for infrared therapy, has many positive effects like detoxification, reducing muscle tension, improving circulation, relaxation, boosting immune system, lowering blood pressure and lowering side effects of diabetes
• Visible spectrum


  The range of electromagnetic spectrum that the eyes can detect, ranges from 4.3 x 10 to 7.5 x 10 hertz, includes colors from red to violet, travels at same speed but differs in wavelength, energy and frequency, when all frequencies are fused it appears as white light
• Too much light focused on the eyes can damage or burn the retina causing the blurring of vision or even blindness
• Ultraviolet radiation


  Has higher energy and frequency than visible light, used to sterilize medical instruments, produce vitamin D, sterilize drinking fountains, identify bank notes, used in LASIK eye surgery, treating skin diseases, gathering information about celestial bodies
• Ultraviolet radiation


  • Over exposure can damage tissue, burn skin or cause skin cancer, damage eyes, use UV sunscreen/sunblock lotions, eyeglasses that filter the frequencies, limit sunlight exposure from 10am to 4pm to avoid the damaging effect
• 1. rays


  Have very short wavelengths but with higher frequency and energy than UV, can pass through certain barriers, long wavelength X-rays can penetrate flesh but not bone, short wavelength X-rays can penetrate even metals, used for diagnosing bone fractures and tumors
• 1. rays

  • Can damage body tissues, frequent/overexposure can cause cancer
• Gamma rays


  Electromagnetic waves with the highest frequency and energy, emitted by stars and some radioactive substances, can only be blocked with lead and thick concrete, very strong that they can kill living cells, used to treat cancer through radiotherapy, also used for drinking water sterilization and medical equipment
• Scientists and their contributions

  • Heinrich Hertz - Radio waves
  • James Clerk Maxwell - Microwaves
  • Frederick William Herschel - Infrared
  • Isaac Newton - Visible Spectrum
  • Johann Wilhelm Ritter - Ultraviolet rays
  • Wilhelm Ronald Roentgen - X-rays
  • Paul Ulrich Villard - Gamma rays
• What happens to EM radiation when it encounters a barrier

  • It can bounce (reflectance or scattering), pass through (transmittance), or just plain stop (absorbance)
• Radiation damage


  Acute effects that occur within one or two months after exposure, Delayed or long-term effects that appear in months or years (e.g. Leukemia and formation of cancer tumors)
• Extent of radiation damage

  • Determined by dose level, degree of exposure, organ sensitivity, time length
• Materials used to detect radiation

  Geiger counter, Film badge, Thermoluminescent dosimeter or TLD