Lecture Notes on Waves, Forces, Energy, and Electricity

Waves

• Energy Transfer: Waves transfer energy without transferring matter.
• Types of Waves:
  • Transverse Waves: Particles oscillate perpendicular to direction of energy transfer (e.g. light, EM waves).
  • Longitudinal Waves: Particles oscillate parallel to direction of energy transfer (e.g. sound waves).

Wave Properties

• Wavelength (λ): Distance between peaks.
• Amplitude: Maximum displacement from equilibrium.
• Time Period (T): Time for one complete wave to pass.
• Frequency (F): Number of complete waves passing a point per second.
  • Formula: F = 1/T
• Wave Speed (V): Formula: V = Fλ

Wave Phenomena

• Polarization: Transverse waves can be polarized, allowing only waves oscillating in a certain direction.
• Interference: When two waves meet, they can interfere constructively (amplitude increases) or destructively (cancels out).
  • Harmonics:
    • First harmonic: λ = 2L (L = length of string).
    • Second harmonic: λ = L.
• Diffraction: Occurs when waves pass through a slit and spread out.
  • Young's Double Slit Experiment: Uses coherent sources to create interference patterns.
    • Fringe width (W) formula: W = λD/S (D = distance to screen, S = slit separation).

Refraction

• Snell's Law: n₁ sin(θ₁) = n₂ sin(θ₂) (n = refractive index).
• Total Internal Reflection (TIR): Occurs when angle of incidence exceeds the critical angle.

Forces and Motion

• Newton's Laws:
  • 1st Law: An object's motion remains constant unless acted upon by an external force.
  • 2nd Law: F = ma (Force = mass × acceleration).
  • 3rd Law: For every action, there is an equal and opposite reaction.
• Weight: W = mg (g = gravitational field strength, ~9.81 m/s²).
• Equilibrium: No resultant force or moment.
• Energy:
  • Kinetic Energy (KE): KE = 1/2 mv²
  • Gravitational Potential Energy (GPE): GPE = mgh
  • Work Done (E) = F × d (Force × distance).

Energy and Work

• Power: P = Fv (Power = force × velocity).
• Hooke's Law: F = kx (k = spring constant, x = extension).
  • Young's Modulus: E = stress/strain.

Electricity

• Ohm's Law: V = IR (Voltage = current × resistance).
• Current and Voltage:
  • Current (I) = Q/T (Charge/time).
  • Voltage (V) = Energy/Charge.
• Power in Circuits: P = IV, P = I²R, P = V²/R.
• Kirchhoff's Laws:
  • 1st: Current in = Current out at junctions.
  • 2nd: Sum of EMFs = Sum of PD drops in a closed loop.
• Series & Parallel Circuits:
  • Series: Total Resistance = R₁ + R₂.
  • Parallel: 1/R_total = 1/R₁ + 1/R₂.

Particle Physics

• Types of Particles:
  • Hadrons (made of quarks): Baryons (3 quarks) and Mesons (quark + antiquark).
  • Leptons: Fundamental particles (e.g. electrons).
• Forces:
  • Electromagnetic: Exchanged by virtual photons.
  • Strong Nuclear: Keeps nucleus together; gauge bosons (pions/gluons).
  • Weak Nuclear: W and Z bosons.
  • Gravity: Gravitons (not yet observed).

Quantum Physics

• Photoelectric Effect: Demonstrates light's particle nature.
  • Equation: E_k(max) = hf - φ (φ = work function).
• De Broglie Wavelength: λ = h/p (h = Planck's constant, p = momentum).
• Fluorescent Tubes: Use thermionic emission to excite mercury gas, emitting UV light which induces visible light in the coating.