L2_A
       What are waves?
       The 1-d wave equation and its solution
       Proof that f (x ± vt) solves the wave equation

L2_B
       What are waves?
       Simple solution to the wave equation
       Definitions: Amplitude and Absolute phase
       The phase velocity

L2_C
       Plane waves
       The 3-D wave equation: vectorial!
       Solution to scalar Helmholtz’s equation
       Wave that really moves!

L2_D
       Why are EM waves transverse?
       The magnetic field direction?
       The strength of magnetic-field?
       Light is transverse electromagnetic wave
       Spherical wave

L2_E
       The energy of waves
       The energy density of lightwave
       The Poynting vector
       The irradiance (often called the intensity)