electromagnetic waves

• What type of waves are electromagnetic (EM) waves?

  Transverse waves
• What do EM waves transfer from their source to an absorber?

  Energy
• How are EM waves grouped?

  By their wavelengths and frequencies
• What is the speed of EM waves in a vacuum?

  $3 \times 10^8 \text{ m/s}$
• What happens to EM waves when they pass through different substances?

  They may absorb, transmit, refract, or reflect
• What is refraction in terms of EM waves?

  Change in velocity of EM waves in substances
• What does a ray diagram illustrate about EM waves?

  How waves change direction at boundaries
• What happens to a refracted ray if it slows down crossing a boundary?

  It bends towards the normal
• What occurs when a wave travels at a right angle to the boundary?

  It changes speed but not direction
• What do wave front diagrams represent?

  Change of speed when crossing substances
• What happens to wave fronts when a wave slows down crossing a boundary?

  They become closer together
• How does a wave change direction when crossing a boundary at an angle?

  One end changes speed before the other
• What can produce EM waves?

  Changes inside an atom or nucleus
• How are gamma rays produced?

  By changes in the nucleus of an atom
• How can radio waves be produced?

  By oscillations in an electrical circuit
• How can we detect radio waves?

  They create an alternating current in receivers
• What are radio waves used for?

  Transmitting television and mobile signals
• What are microwaves used for?

  Satellite communications and cooking food
• What is infrared radiation used for?

  Heating and infrared cameras
• Which types of EM waves are harmful to humans?

  Ultraviolet, X-rays, gamma rays
• What are the hazards of ultraviolet radiation?

  Damage skin cells and increase cancer risk
• Why are X-rays used for medical imaging?

  They pass through flesh but not bone
• Why are gamma rays used for treating cancer?

  High doses kill cells and bacteria
• What is refraction?

  Waves change speed and direction at boundaries
• What happens to the direction of a refracted EM wave when it slows down?

  It bends towards the normal
• What are the key terms related to electromagnetic waves?

  • Alternating current
  • Electromagnetic wave
  • Radiation dose
  • Ray diagram
  • Electromagnetic spectrum
  • Reflection
• What is the definition of radiation dose?

  Risk of harm from radiation exposure
• Why are EM waves not mechanical waves?

  They can travel through a vacuum
• What is the order of EM waves by decreasing wavelength?

  Radio, microwave, infrared, visible, ultraviolet, X-rays, gamma
• Which part of the EM spectrum can humans see?

  Visible light
• How do electrons in an atom emit EM waves?

  By moving down between energy levels
• What is the purpose of a ray diagram?

  To illustrate the path of EM waves
• What is the significance of the wave front in wave front diagrams?

  It represents the direction of wave movement
• What happens to the wave fronts when a wave speeds up crossing a boundary?

  They become further apart
• What is the effect of high doses of gamma rays?

  They can kill living cells
• What is the role of infrared sensors?

  To detect infrared waves emitted by hot objects
• How do EM waves interact with different materials?

  They can be absorbed, transmitted, refracted, or reflected
• What is the relationship between wavelength and frequency in the EM spectrum?

  Longer wavelengths correspond to lower frequencies
• What is the significance of the electromagnetic spectrum?

  It encompasses all types of EM waves
• What can produce EM waves of various frequencies?

  Changes inside an atom or nucleus