P6

Cards (44)

  • Light
    A particle, a wave or both a particle and wave
  • Light has been studied extensively but its fundamental nature is still a mystery
  • Before the 19th century
    Light was considered to be a stream of particles either emitted by the object being viewed or emanating from the eyes of the viewer

  • Formulated the corpuscles theories in support of the particle nature of light
  • Thomas Young
    Provided a clear demonstration of the wave nature of light in 1801
  • Light rays interfere with each other under appropriate conditions, which could not be explained by a particle theory at that time
  • Maxwell
    His work was the most important that led to the acceptance of the wave theory of light during the 19th century
  • Maxwell
    Asserted that light is a form of high frequency electromagnetic wave
  • Hertz
    Proved Maxwell's conclusion by producing and detecting electromagnetic waves in 1887
  • Hertz discovered the photoelectric effect which contradicted the wave theory
  • Einstein
    Proposed an explanation of the photoelectric effect in 1905 using the concept of quantization developed by Max Planck in 1900
  • Quantization model

    Assumes that the energy of a light wave is present in particles called photons; hence energy is said to be quantized
  • Einstein's theory
    The energy of a photon is proportional to the frequency of the electromagnetic wave
  • Light can behave like a particle and like a wave depending on the experiment used to study it
  • Light is a wave can be seen in some experiments involving the interference of light through single and double slits
  • Einstein showed that light also behaved like a particle, or photon, in a manner that could only be explained by particle theory
  • These developments led to a conclusion that light has a dual nature: LIGHT AS A PARTICLE AND A WAVE
  • Light ray
    A thin beam of light
  • Umbra
    The darker part of a shadow
  • Eclipse
    • An example of shadow formation when light coming from the sun hits an opaque barrier such as moon and Earth
  • Transverse wave
    The direction of the wave is perpendicular with the particle
  • Characteristics of a transverse wave
    • Crest
    • Trough
    • Period
    • Frequency
    • Amplitude
    • Wavelength
  • Wave speed formula
    Wave Speed (v) = Wavelength / Period
  • For light, v = c (the speed of light in a vacuum)
  • Nothing can travel faster than the speed of light in a vacuum but when light travels in a denser material, it slows down
  • Visible light
    The only part of the electromagnetic spectrum that can be seen by the human eye
  • Electromagnetic spectrum
    • Radio waves
    • Infrared
    • Visible light
    • Ultraviolet
    • X-rays
    • Gamma rays
  • Violet has the greatest frequency and energy, while red has the longest wavelength
  • White light
    The presence of all frequencies of visible light
  • Black
    The absence of the visible light spectrum
  • Primary colors of light

    • Red
    • Blue
    • Green
  • Secondary colors of light

    • Yellow
    • Cyan
    • Magenta
  • When the colors of light with varying degrees of intensity are mixed/added, another color will be produced
  • White light can also be formed when the three primary colors with the same intensity are added
  • Complementary colors of light

    • Red + Cyan = White
    • Green + Magenta = White
    • Blue + Yellow = White
  • Specular reflection

    Happens if the reflected light is from a smooth surface, will produce a regular reflection
  • Diffuse reflection

    Occurs if the incident light hits a rough surface
  • Law of reflection
    The angle of incidence is equal to the angle of reflection
  • The normal line is always drawn perpendicular with the reflecting surface. Angle of incidence and reflection is measured from the normal line
  • Multiple reflection of light
    When light hits reflecting surfaces several times, multiple images will be formed