Reflection, absorption & transmission

• Reflection, Absorption & Transmission

  • Depending on the densities of the materials on either side of a boundary, a wave may be:
  • Reflected
  • Transmitted
  • Absorbed
• Reflection

  • Reflection occurs when:
  • A wave hits a boundary between two media and does not pass through, but instead stays in the original medium
  • The law of reflection states:The angle of incidence = The angle of reflection
• Relection:

  A) incidence

  B) reflection

  C) Normal

  D) i

  E) r

  
• Reflection of a wave at a boundary

  • Some of the wave may also be absorbed or transmitted
  • Echos are examples of sound waves being reflected off a surface
  • Flat surfaces are the most reflective
  • The smoother the surface, the stronger the reflected wave is
  • Rough surfaces are the least reflective
  • This is because the light scatters in all directions
  • Opaque surfaces will reflect light which is not absorbed by the material
  • The electrons will absorb the light energy, then reemit it as a reflected wave
• Transmission

  • Transmission occurs when: A wave passes through a substance
  • For light waves, the more transparent the material, the more light will pass through
  • Transmission can involve refraction but is not exactly the same
  • For the process to count as transmission, the wave must pass through the material and emerge from the other side
  • When passing through a material, waves are usually partially absorbed
  • The transmitted wave may have a lower amplitude because of some absorption
  • For example, sound waves are quieter after they pass through a wall
• Absorption

  • Absorption occurs when: Energy is transferred from the wave into the particles of a substance
  • Waves can be partially or completely absorbed
  • Sound waves are absorbed by brick or concrete in houses
  • Light will be absorbed if the frequency of light matches the energy levels of the electrons
  • The light will be absorbed, and then reemitted over time as heat
  • If an object appears red, this means:
  • Only red light has been reflected
  • All the other frequencies of visible light have been absorbed
• Visible light:

  A) white

  B) Red

  C) reflection

  D) absorbed

  
• If the filter contains a colour of light that is present in the object then it will reflect that light. If the colour is not present then it will appear black (absence of light).
• Colour wheel of light

  A) Magenta

  B) Yellow

  C) Cyan

  D) White