2.2. Wave Model (C2)

Similarities:

• All waves transfer energy without transferring matter.

• All waves have basic properties: wavelength (λ), frequency (f), amplitude, speed (v), and period (T).

• All obey the wave equation: v=fλ

Differences:

• Mechanical Waves include sound, water waves, seismic waves. Medium required (e.g., air, water, string). Speed depends on properties of the medium.  Electromagnetic Waves  include light, X-rays, radio waves. No medium required (can travel through vacuum).  Speed depends on medium (if present), but can travel in space

• Transverse Waves include light, water waves, waves on a string. Particle motion perpendicular to wave direction. Longitudinal Waves include sound, compression waves in a spring. Particle motion parallel to wave direction

A wave is a disturbance that propagates through a medium (or space) due to oscillating particles or fields.

These oscillations cause neighboring particles or points in the medium to oscillate — energy gets transferred, but the medium itself doesn’t move with the wave.

In the wave model:

• Amplitude relates to energy (higher amplitude → more energy).

• The speed depends on the medium's properties (e.g., tension in a string, density of air).

For mechanical waves, energy moves through inter-particle interactions. For EM waves, energy travels through oscillating electric and magnetic fields.

From the wave equation v=fλ

• If frequency increases (and speed stays constant): Wavelength decreases → higher pitch for sound, or shift toward blue in light.

• If the wave enters a new medium: Speed changes (depending on medium properties like density or stiffness).  Frequency stays the same (set by the source). So, wavelength must change to maintain v=fλ

Example: When light enters water from air: Speed decreases, frequency stays the same ⇒ wavelength shortens.