PHYSICS Q4 week 2

• Maxwell's Equations describe light as a propagating wave made up of electric and magnetic fields
• Maxwell's wave equation shows that the speeds of the waves depend on the combination of constants involved in electrostatics and magnetism
• Electromagnetic wave


  A transverse wave produced by a vibrating electric charge
• Electromagnetic waves


  • Possess the characteristics of wavelength, frequency, and speed
  • Can propagate through a vacuum, unlike sound waves
• Index of refraction


  A property of a medium that dictates how EM waves will propagate
• Electric permittivity


  Related to the energy stored in an electric field
• Magnetic permeability


  Related to the energy stored in a magnetic field
• Regular reflection


  Reflected rays have only one direction
• Diffused reflection


  Reflected rays have varying directions
• Total internal reflection (TIR)


  Reflection of the total amount of incident light at the boundary between two media
• TIR occurs when the angle of refraction reaches 90 degrees before the angle of incidence reaches 90 degrees
• TIR only occurs with large angles of incidence, larger than the critical angle
• Critical angle


  The angle of incidence at which total internal reflection occurs, depends on the two materials at the boundary
• Applications of total internal reflection

  • Optical fibers
  • Decorative lamps
  • Glass fibers for communication
  • Endoscopes
• Hands-on experiment on reflection

  1. Prepare experimental setup

  2. Draw straight line on bond paper

  3. Place mirror on line

  4. Shine light on mirror at different angles

  5. Observe reflected rays
• Optical fiber


  A thin rod of high-quality glass that can carry more information than an ordinary cable of the same thickness
• Very little is absorbed by the glass in optical fibers
• Signals in optical fibers do not weaken as much over long distances as the signals in ordinary cables
• Applications of optical fibers

  • Decorative lamps
  • Glass fibers (used for communication technologies)
  • Endoscopes (used to view human body's internal organs)
• Optical fibers are found in decorative lamps, glass fibers (used for communication technologies), and endoscopes (used to view human body's internal organs)
• Optical fiber


  • Thin rod of high-quality glass
  • Carries more information than ordinary cable of same thickness
  • Signals do not weaken as much over long distances as in ordinary cables
• Figure 9 shows an optical fiber
• Hands-on Experiment on Reflection

  1. Prepare experimental set-up

  2. Draw straight horizontal line and perpendicular line on bond paper

  3. Designate intersection point as A
• Objective of the experiment is to perform a simple ray optics and reflection experiment
• Materials used: bond paper, pen, ruler, protractor, mirror, push pin, graphing paper
• Wavelength


  The distance between successive crests or troughs of a wave
• Transverse wave


  A wave where the movement of the energy is perpendicular to the movement of the particle of the wave
• Electric permittivity


  A property of a medium that dictates how EM waves will propagate, related to the energy stored in an electric field
• EM waves are transverse waves that have the capability of propagating even without a medium
• Maxwell's equations provide an important link among the concepts of electricity, magnetism and light, and explain how light behaves as it propagates
• When a ray of light enters from denser medium to rare medium

  It bends away from normal
• Cladding


  The outer concentric shell in fiber optic
• Total internal reflection of light


  The entire light is reflected into the denser medium
• The critical angle for water-air boundary is 48 degrees
• For total internal reflection to occur, the index of refraction must decrease across the boundary in the direction of light refraction, and the angle of incidence of the light ray must not exceed the critical angle of the interface
• Light is confined within the core of a simple optical fiber by total internal reflection at the core cladding boundary
• Angle AON is the angle of incidence in the diagram showing total internal reflection
• Angle AON = angle BON in the diagram showing total internal reflection
• Angle AON must be the critical angle in the diagram showing total internal reflection
• Magnetic wave


  Disturbance (in the form of waves) propagating through the EM field in accordance with EM laws