dual nature of light

• corpuscular theory

  • isaac newton
  • light is made up of particles called corpuscles
• corpuscles

  • emitted from luminous sources such as the sun, candle, and electric lamp.
  • always travel in a straight line in all directions
  • perfectly elastic
  • travel faster in the DENSER MEDIUM than in the rarer medium (proven wrong)
• example of corpuscles


  travels faster in water than in air
• reflection

  • tendency of light to bounce off things
  • angle of incident corpuscles is equal to the angle of reflected corpuscles
• refraction

  • does not bounce off
  • passes through the medium
  • change in direction
• limitations of the corpuscular theory

  • light travels faster in a denser medium than in the rarer medium
  • assumption that the different colors of light are due to the differences in the sizes of corpuscles has no justification
  • cannot explain the diffraction and interference of light


  light travels faster in RARER MEDIUM

  light colors are due to wavelengths in the electromagnetic spectrum
• wave theory

  • christian huygens
  • wave as a nature of light
  • light is a series of waves in all directions
• longitudinal waves

  • wavelengths are moving parallel to the direction of light (ex: sound waves)
• transverse waves

  • move perpendicular to the direction of the propagation of the wave (ex: ripples formed on the surface of water.)
  • light behaves as a transverse wave
• dual nature of light

  light sometimes behaves as a wave and sometimes as a particle, but it cannot both behave at the same time.
• wave nature of light

  diffraction and interference
• particle nature of light 


  reflection and refraction
• 1. Thomas young's-double-slit experiment

  • monochromatic light is shone on a screen containing two very tiny slits, which result in a series of bright and dark bands
  • considered interference
• 1. diffraction

  • light passes through a slit or hole
  • LARGER the slit, the LESS wave patterns.
  • SMALLER the slit, MORE wave patterns.
  • prism- has tiny holes or slits
• 1. interference

  • two waves move through the same medium
  • produces different wave patterns of light fringes and dark fringes
• constructive interference 


  produces light fringes from two interfering light rays
• destructive interference 


  dark fringes from interfering light waves
• application of interference 


  thin-film interference in a soapy bubble- once light enters a bubble, it produces different colors due to diffraction
• 1. Hertz and Einstein's photoelectric effect

  • light shining on a material causes the emission of electrons from that material (ex: photosynthesis)
• 1. reflection

  • law of reflection- the angle of incidence is equal to the angle of reflection
  • all reflections have equal angles of incidence
• specular reflection 


  CLEAR image because of perfect surface
• diffused reflection


  BLURRY image because of the bumpy surface (ex: water is not perfectly smooth)
• 1. refraction

  • bending of light as it enters from one medium to another
  • angles of incidence and refraction are not equal because light changes direction
  • HIGHER INDEX of refraction, the HIGHER the BENDING of light.

  (ex: pencil in a glass of water)
• electromagnetic spectrum

  • wave nature of light
  • the entire range of electromagnetic radiation
  • encompasses all the different types of light that exist
• wavelength

  • distance between two corresponding points in a light wave
  • waves have the highest and lowest points
  • wavelength of light is LONGER, the energy is LOWER

  (ex: UV and gamma rays have higher energy than microwaves and radiowaves)
• electromagnetic radiation 


  form of energy from the light that travels in waves and carries energy throughout space
• ionizing radiation

  • SHORTER wavelength
  • changes the electron configuration of an atom
  • type of radiation released from atoms
  • remove electrons out of atoms and molecules it interacts with.
  • alters atomic structure by removing or manipulating electrons in the material's atoms
• examples of ionizing radiation

  x-rays, uv rays
• non-ionizing radiation

  • LONGER wavelengths
  • type of radiation that does not have enough energy to remove electrons from atoms
  • do not have enough energy to alter the atomic structure of objects
• example of non-ionizing radiation

  visible spectrum of light

  • portion of the electromagnetic spectrum that is detectable by the human eye