General Wave Motion

Waves vs Particles Particles can collide: stick together or bounce off each other Waves pass through each other, either adding up or canceling out: superposition Since (most) waves are ultimately made up of particles, how does superposition happen? WAY too much for us! Now: Lots of jargon... 

Wave motions Wave pulse: One (and only one) pulse moves in a “wavy” fashion. Wave train: A collection of many pulses. Sinusoidal wave: A wave train of a very particular type, and the one which we will consider [not (too) mathematically].

Fig , p.310

Types of waves Transverse waves: particles that make up the wave are moving perpendicular to the motion of the wave. (Waves on a string) Longitudinal waves: particles that make up the wave are moving in the same direction as the motion of the wave. (Sound waves) Others: combination of transverse and longitudinal (Water waves)

Fig. 16-1, p.324

Superposition Waves pass through each other and add up: Constructive Interference Waves pass through each other and cancel out: Destructive Interference

Fig , p.310

Fig , p.308

“Sinusoidal” waves Defined by wavelength “λ”; period “T”, frequency “f”, amplitude “A”, and speed “v”. f = 1/T and v = λ/T so v = fλ. This last equation is true for ALL sinusoidal waves, although “v” is determined by the particular type of wave.

Fig , p.310

“v” determined by what is waving Waves on a string: v = √(T/μ) “μ” is the mass density of the string, and “T” is the tension in the string. Sound waves: v ≈ 340 m/s near the ground on earth; actual value depends on many things. Electromagnetic waves: v = c = 3 × 10 8 m/s