General Properties of Waves

A wave is the transfer of energy without transferring matter, as molecules vibrate but don't move along with the wave.

Mechanical vs. Electromagnetic: Mechanical waves (e.g., sound) need a medium; electromagnetic waves (e.g., light) do not.
Transverse vs. Longitudinal:
- Transverse: Particles vibrate perpendicular to wave motion (e.g., electromagnetic waves, water waves). Peaks are crests, and valleys are troughs.
- Longitudinal: Particles vibrate parallel to wave motion (e.g., sound). They consist of compressions and rarefactions.
Seismic Waves: Earthquakes produce both longitudinal (P-waves, primary, underground) and transverse (S-waves, secondary, surface) waves.

Wave Front: A line representing the crest of a wave.
Amplitude: Maximum displacement from the mean position; represents energy in a wave.
Wavelength: Distance between two successive crests or troughs, or the distance traveled during one complete oscillation.
Period: Time taken for one complete oscillation.
Frequency: Number of oscillations per unit time (Hertz).
Wave Speed: $V = F \cdot \lambda$

Reflection: Change in direction when a wave hits a surface. The angle of incidence equals the angle of reflection.
- Law of reflection states that the angle of incidence is equal to the angle of reflection, or $i = r$ . These angles are always measured from a line, that is perpendicular to the surface $90^{\circ}$ .
Refraction: Change in speed when the medium changes; frequency remains constant.
- Less dense to more dense: Speed and wavelength decrease; bends closer to the normal.
- More dense to less dense: Speed and wavelength increase; bends away from the normal.
- If a wave hits the surface at $90^{\circ}$ , it doesn't bend.
Diffraction: Spreading of a wave as it passes through a gap or around an edge.
- Smaller gap or larger wavelength: Spreads more.
- Larger gap or smaller wavelength: Spreads less.

Mechanical and Longitudinal: Needs a medium and consists of compressions and rarefactions.
Pressure Variation: Compressions increase air pressure, rarefactions decrease it.
Speed of Sound: Air (330 m/s), water (1,500 m/s), steel (5,000-6,000 m/s).
Speed Measurement: Use a smoke pistol to measure the distance and time the sound travels.
Amplitude: Affects loudness.
Frequency: Affects pitch.
Human Hearing Range: 20 Hz to 20,000 Hz; infrasound is below 20 Hz, ultrasound is above 20,000 Hz.

The time taken to hear an echo is the time taken for the sound to travel to the reflecting surface and back.
Distance calculation: $speed = (2 \cdot distance) / time$

All electromagnetic waves can travel through a vacuum at the same speed ( $3 \cdot 10^8$ m/s) and are transverse.
Ordered by frequency (increasing) and wavelength (decreasing).
Harmful high-frequency waves: Gamma rays, X-rays, ultraviolet.
- Visible Light (ROYGBIV):
  - Red, Orange, Yellow, Green, Blue, Indigo, Violet

Microwaves are used for satellite communication.
Low-Orbit Satellites: Phones.
Geostationary Satellites: Broadcast TV; orbit the Earth around the equator in 24 hours.

Digital: Two values (high/low).
Analog: Any value within a range.
Digital is preferred for data transmission and range as it is less affected by noise.