Properties of Light

Nature of Light

• Light travels in two primary forms:
  • Wave Nature
    • Light behaves like a wave.
    • High frequency: Waves close together.
    • Low frequency: Waves farther apart.
    • Electromagnetic Spectrum
      • Ranges from gamma rays (high frequency) to radio waves (low frequency).
      • Visible light is located in the middle of the spectrum.
      • Wavelength and color correlation: Specific colors are associated with specific wavelengths (400-700 nm).
  • Particle Nature
    • Light travels as photons (particles).
    • Wave-particle duality: Light exhibits properties of both waves and particles.

Key Constants and Variables

• Speed of Light (c):
  • Constant value: 3.00 x 10^8 m/s.
• Wavelength (λ):
  • Distance between similar points on a wave.
  • Measured in nanometers (nm), converted to meters (m) for calculations.
• Frequency (f or v):
  • How often a wave occurs.
  • Measured in Hertz (Hz), equivalent to 1/s.

Important Equations

• Speed of Light Equation:
  • c = λ x f
• Energy Equation:
  • E = hf (or E = hv)
  • Planck’s Constant (h): 6.626 x 10^-34 Joules x seconds.
  • Frequency in Hertz helps calculate energy in Joules.
• Combined Equation for Energy and Light:
  • E = (hc)/λ
  • Combines the speed of light and energy equations, eliminating frequency.

Applications and Phenomena

• Photoelectric Effect:
  • Demonstrates that light behaves as particles by ionizing electrons from metal surfaces.
• Bohr Model of the Atom:
  • Energy levels correspond to wavelengths and colors observed.
  • Electron transitions between energy levels involve absorbing or emitting energy.
  • Allows calculation of energy from observed wavelengths and colors.

Practical Example

• To calculate wavelength for a given frequency:
  • Use c = λ x f to solve for λ.
  • Example: Frequency of 5.4 x 10^14 Hz yields a wavelength of 5.56 x 10^-7 m.
• Importance of using proper calculator functions to handle exponents correctly.

This summary captures the dual nature of light, essential equations, and their applications, providing a comprehensive overview for further study and problem-solving.