PHYSCI semi

• Light has no mass and is not really considered matter
• Light


  It behaves like both a particle and a wave
• Light as a Particle (energy)


  • According to Albert Einstein
  • It behaves like a particle because it's made of tiny packets of energy (photons)
  • Photons is a discrete bundle of electromagnetic energy moving at the speed of light, has no rest mass but has momentum, and carries energy
  • This "particle" nature of light explains how it can carry energy and interact with matter, like when sunlight warms your skin or when light triggers chemical reactions in plants during photosynthesis
• Light as a Wave (area and energy)

  • According to James Maxwell
  • Light behaves like a wave because it can spread out and interfere with itself
  • Electromagnetic waves and light waves are essentially the same thing. Light is a type of electromagnetic wave that we can see with our eyes, but the electromagnetic spectrum includes a wide range of waves beyond what we can see
• Specification/types of Electromagnetic Waves

  ü  Low Frequency Wave (low energy)

  ü  High Frequency Wave

   

  Low Frequency Waves

  ·         Radio waves

  ·         Microwaves

  ·         Ultraviolet waves

  ·         Visible light

   

  High Frequency Waves

  ·         X-ray

  ·         Gammarays
• Interaction of Lights

  • Reflect
  • Refract
  • Absorb
  • Scatter
  • Disperse
  • Transmit
• Reflect


  When light bounces back from its source
• Refract


  When light travels from one material into another material and the direction of the light changes (bending of light)
• Absorb


  When a material absorbs (take in) the energy of the light
• Scatter


  Like sunlight bouncing around off tiny things in the air, and how it scatters depends on the size of those things compared to the wavelength of light. (e.x this is what makes the sky blue—air molecules scatter shorter wavelengths of light like blue and violet more than longer ones like red and orange)
• Disperse


  When beam of lights refracts and it produces colors
• Transmit


  When light passes through a material without being absorbed or reflected, allowing us to see through that material
• Thales of Miletus


  Often considered the first philosopher in Western tradition, introduced the concept of naturalistic explanations for phenomena, predicted a solar eclipse suggesting an understanding of celestial motions
• Anaximander of Miletus


  Expanded on Thales' ideas, proposed the concept of the "apeiron" - an indefinite and boundless substance from which all things arise and to which they return, created one of the earliest known cosmological models with concentric spheres
• Pythagoras


  Primarily known for contributions to mathematics, extended mathematical principles to cosmology, believed in a spherical Earth and posited a concept of celestial harmony where the movements of the planets and stars followed mathematical relationships
• Anaxagoras


  Proposed that the Moon shines by reflecting light from the Sun, a departure from earlier beliefs that the Moon generated its own light
• Plato


  Proposed a geometric construction of the universe based on the five Platonic solids, each representing one of the classical elements
• Eudoxus


  Developed a sophisticated geometric model to explain the motions of celestial bodies, laid the foundation for later mathematical astronomy and helped refine understanding of planetary orbits
• Aristotle


  Proposed a geocentric model of the universe, with Earth at the center, surrounded by concentric spheres carrying celestial bodies
• Aristarchus


  Proposed a heliocentric model of the solar system, with the Sun at the center and Earth and other planets orbiting around it
• Claudius Ptolemy


  Synthesized astronomical knowledge from Greek and Babylonian sources, presented a detailed geocentric model of the universe which remained influential in Western thought for over a millennium
• Nicolaus Copernicus


  Proposed a heliocentric model of the universe, challenging the geocentric view, in his work "De Revolutionibus Orbium Coelestium"
• Tycho Brahe

  Meticulous observations of the positions of stars and planets were crucial for Kepler's later work, provided the empirical foundation for Kepler's laws of planetary motion
• Johannes Kepler


  Formulated three laws of planetary motion based on Brahe's observations, described the elliptical orbits of planets around the Sun and laid the foundation for modern celestial mechanics
• Light has no mass and is not really considered matter
• Light is unique, it behaves like both a particle and a wave
• Light as a Particle (energy)


  It behaves like a particle because it's made of tiny packets of energy (photons)
• Photons


  • A discrete bundle of electromagnetic energy moving at the speed of light, has no rest mass but has momentum, and carries energy
• This "particle" nature of light explains how it can carry energy and interact with matter, like when sunlight warms your skin or when light triggers chemical reactions in plants during photosynthesis
• Light as a Wave (area and energy)


  Light behaves like a wave because it can spread out and interfere with itself
• Electromagnetic waves and light waves are essentially the same thing
• Light is a type of electromagnetic wave that we can see with our eyes, but the electromagnetic spectrum includes a wide range of waves beyond what we can see
• Albert Einstein: 'Light behaves like a particle'
• James Maxwell: 'Light behaves like a wave'