Q2 science

• Electromagnetic waves


  Waves created as a result of vibrations between an electric field and magnetic field
• EM waves can travel through anything, even in a vacuum (empty space), at a speed of 3x10^8m/s
• Oersted's discovery


  A changing electric field produces a magnetic field
• Faraday's discovery


  A changing magnetic field will produce an electric field
• Characteristics of a wave


  • Crest
  • Wavelength (λ)
  • Trough
  • Amplitude
  • Frequency (Hz)

  
• Types of EM waves


  • Radio wave
  • Microwave
  • Infrared
  • Visible light
  • UV ray
  • X-ray
  • Gamma rays

  
• Radio waves


  • Longest wavelength, lowest frequency, lowest energy
  • Produced by making electrons vibrate in an antenna
  • Size as wide as a basketball court
• Microwaves


  • Used in satellite communications and RADAR
  • Size as big as a coin
• Infrared


  • Lies beyond the red end of the visible light
  • Emitted by all objects
  • Size as big as the tip of a pin
• Visible light


  • The only visible EM wave
  • Proves that white light is composed of different colors
  • Size as big as a bacteria
• UV rays


  • Lie beyond the violet end of the visible spectrum
  • Give a tanning effect
  • Size as big as a molecule
• 1. rays


  • Come after the UV rays but carry higher energy
  • Used in detecting bone fractures
  • Size as big as an atom
• Gamma rays


  • Lie at the end of the electromagnetic spectrum
  • Shortest wavelength, highest frequency, highest energy
  • Most dangerous of all EM waves
  • Size as big as atomic nuclei

  
• Terrestrial Communication


  • Cell phones use microwaves
• Cooking


  • Microwaves in a microwave oven penetrate and agitate water molecules, creating heat to cook food
• RADAR


  • A detection system used to determine the range, angle, or velocity of objects
• Thermal imaging through infrared scanners


  • Used to show temperature variation of the body
• Remote control (IR Remote)


  • Uses LED lights to transmit signals to control devices
• Night vision goggles


  • Use thermal imaging technology to capture infrared light being emitted as heat
• Visible light


  • Enables us to see things around us
  • Provides light to screens of electronic devices
  • Artificial lights like flashlights and lamps
• Optical fibers


  • Used in endoscopes to observe internal parts of the body
• Ultraviolet B (UVB) radiation


  • Interacts with skin protein to produce vitamin D3
• Security markings


  • Sensitive documents include a UV watermark
• Sterilization of water in drinking fountains


  • Ultraviolet light disinfection removes microbiological contamination
• Fluorescence


  • Washing powder contains fluorescent chemicals that glow in sunlight
• Diagnosing bone fracture


  • X-rays can penetrate flesh but not bones
• Airport security scanner


  • Short wavelength x-rays can penetrate through metals
• Treat tumors and cancer


  • High-energy gamma rays destroy cancer cells
• Sterilization of surgical instruments


  • Gamma rays easily penetrate materials and kill bacteria and microorganisms
• Non-ionizing radiation


  Does not have enough energy to remove electrons from atoms and molecules
• Ionizing radiation


  High-energy EM waves like x-rays and gamma rays that can alter molecules within cells
• Excessive exposure to ionizing radiation can cause skin or tissue damage, cancer, and death</b>
• Improper handling of radioactive materials can lead to radioactive pollution
• Reflection


  The bouncing off of light on a surface

  
• Mirror


  A surface that reflects light without diffusion and produces an image

  
• Law of reflection


  1. Incident ray, reflected ray, and normal line lie in the same plane

  2. Angle of incidence = angle of reflection

  
• Characteristics of images formed by a plane mirror

  • Virtual

  Same size as object

  Same orientation as object

  Same distance from mirror as object

  
• Specular/Regular reflection


  Light reflected from a smooth surface at a definite angle

  
• Diffused/Irregular reflection


  Light reflected from rough surfaces in all directions

  
• Multiple reflections


  Parallel mirrors produce infinite images

  Two mirrors at 180° reflect once

  Two mirrors between 180° and 90° reflect twice

  Two mirrors at 90° reflect twice and one composite

  Angle less than 90° shows two straight and two partial reflections

  At 72° there are 4 complete reflections

  At 60° there are 5 reflections (4 straight, 1 composite)

  At 45° there are 7 reflections (3 in each mirror, 1 composite)