P12 ELECTROMAGNETIC WAVES

• What type of waves are electromagnetic waves?

  Transverse waves
• What is the speed of electromagnetic waves in a vacuum?

  The speed of light
• How are electromagnetic waves grouped?

  By their energy levels, from low to high
• What can different substances do to electromagnetic waves?

  Absorb, transmit, reflect, or refract waves
• What can very short wavelength light waves, such as ultra-violet, do?

  They can damage cells
• What is refraction?

  It occurs when there is a difference in the velocity of the wave in different substances
• What do ray diagrams illustrate in the context of refraction?

  They show what happens when a wave is refracted at the boundary between two different substances
• What happens to a refracted ray if a wave slows down when crossing a boundary?

  The refracted ray bends toward the normal
• What happens to a refracted ray if a wave speeds up when crossing a boundary?

  The refracted ray bends away from the normal
• What occurs when a wave travels at a right angle to the boundary?

  It will change speed but not direction
• What do wavefront diagrams explain in terms of refraction?

  They explain the change of speed that occurs when a wave travels from one substance to another
• What is a wavefront?

  An imaginary line at right angles to the direction the wave is moving
• What happens to wavefronts if a wave slows down as it crosses a boundary?

  The wavefronts become closer together
• What occurs when a wave crosses a boundary at an angle?

  One end of the wavefront changes speed before the other, causing the wave to change direction
• What are the key points of refraction of electromagnetic waves?

  • Refraction occurs due to a difference in wave velocity in different substances.
  • Ray diagrams illustrate the bending of waves at boundaries.
  • If a wave slows down, it bends toward the normal.
  • If a wave speeds up, it bends away from the normal.
  • Waves traveling at right angles change speed but not direction.
• How do wavefront diagrams help in understanding refraction?

  • They represent the change of speed when a wave crosses a boundary.
  • Wavefronts become closer together if the wave slows down.
  • Crossing a boundary at an angle causes one end of the wavefront to change speed first, altering direction.
• What are some uses of electromagnetic (EM) waves?

  Television and radio signals
• Which application of EM waves is used for satellite communications?

  Satellite communications
• What is one use of EM waves in cooking?

  Electrical heaters
• How are EM waves used in medical imaging?

  For medical imaging and treatments
• What is the purpose of fibre optic communications?

  To transmit data using light signals
• How do energy-efficient lights utilize EM waves?

  They use EM waves to produce visible light
• What is the role of EM waves in artificial sun tanning?

  They provide UV radiation for tanning
• What is one application of EM waves in infrared technology?

  Infrared cameras
• What type of communication uses EM waves?

  Satellite communications
• Why are EM waves important for energy-efficient lights?


  They help in producing light with less energy consumption
• How do EM waves contribute to medical treatments?

  They are used in imaging and therapeutic procedures
• How do the uses of EM waves in cooking and medical imaging differ?

  Cooking uses heat, while medical imaging uses diagnostic techniques