PHYSCI PLEASE LET ME SLEEP

• Wave-particle theory


  Idea that light behaves as both a wave and a particle
• Christiaan Huygens


  • Proposed a wave theory of light
• Isaac Newton


  • Proposed a particle theory of light
• Newton's particle theory was accepted for over a century due to his fame
• Thomas Young's double slit experiment revealed the wave activity of light, implying the wave theory prevailed over particle theory
• In 1905, Albert Einstein hypothesized that light travels in discrete bundles of energy
• Wave model of light

  Light is a form of electromagnetic wave that propagates through space by oscillations of electric and magnetic fields
• Wave model of light

  • Explains phenomena such as interference and diffraction
• Diffraction


  1. Light travels in wakes

  2. Light can bend around obstacles
• Interference


  Occurs when waves interact with each other
• Reflection


  Light waves strike a smooth surface and reflect according to the law of reflection
• Refraction


  Light waves pass from one medium to another and change direction due to a change in speed

  
• Particle model of light

  Light is viewed as a stream of particles called photons that travel in straight lines and transfer energy and momentum
• Reflection (particle model)


  Photons are absorbed and re-emitted by the atoms in the material, with the angle of reflection equal to the angle of incidence
• Refraction (particle model)


  Photons interact with the atoms in the material, causing them to change direction due to a change in speed
• Photon


  An elementary particle that constitutes the basic electromagnetic radiation, including visible light. It is a particle without mass and electric charge, but it carries energy and momentum. It behaves both as a particle and a wave, and its energy is directly related to the frequency of the electromagnetic radiation to which it belongs.
• Photons


  • Responsible for transmitting light energy, enabling vision, and playing a fundamental role in processes such as photosynthesis, photography and light-based communication technologies, such as fiber optics
• Red light in photographic dark rooms

  Red light has a lower frequency and lower energy compared to other colors, making it less likely to interact with light-sensitive chemicals in photographic materials
• Sunburn in ultraviolet light vs. visible light

  Ultraviolet (UV) light has higher frequency and higher energy photons that can penetrate deeper into the skin and cause damage, while visible light photons do not have enough energy to cause sunburn
• Seeing colors


  The colors we see are a result of how our eyes perceive different frequencies of light, with specialized cells called cones sending signals to the brain to interpret the different colors

  
• Thomas Young


  • Presented a serious challenge to Newton's ideas on the nature of light
• Davisson and Germer experiment

  • First experimental evidence to support the de Broglie hypothesis: a particle of matter can be both a particle and a wave
• Light is a wave and a particle at the same time
• Dispersion


  Separation of white light into its seven color components when there is a refraction or bending of light
• Light scattering


  The ability of particles to absorb light and scatter it in all directions, with smaller particles scattering shorter wavelengths (high frequency) and larger particles scattering longer wavelengths (low frequency)
• Rayleigh scattering


  Scattering of light by particles much smaller than the wavelength of light
• Mie scattering


  Scattering of light by particles comparable in size to the wavelength of light
• Diffraction


  Bending of light when it encounters an obstacle or an opening, resulting in the formation of shadows and diffraction fringes
• Relationship between diffraction and obstacle size

  Inversely proportional: as the size of the obstacle increases, the amount of diffraction decreases, and vice versa
• Interference


  Superposing of waves from different sources, resulting in interference patterns
• Constructive interference


  Occurs when two identical parts of two waves meet, such as a crest of one wave meeting the crest of another wave of the same wavelength, resulting in a new wave with the same wavelength but twice the amplitude
• Destructive interference


  Occurs when two opposite parts of two waves meet, such as the crest of one wave meeting the trough of another wave, resulting in the cancellation of the two waves