• Sound waves = Longitudinal waves
• They can move through
  • Gases 🌬️
  • Liquids 🌊
  • Solids 🌲

Fun Fact: When you listen to your favorite song on your phone, it's sound waves traveling from your device to your ears!

• Gases
  • Can't sustain displacement at right angles to the energy direction.
  • Why? No restoring force.
• Liquids
  • Only at their surfaces can they sustain displacement at right angles.
• Solids
  • Can transmit both transverse and longitudinal waves.
  • Why? Atoms and molecules are bonded.

Real-world Example: Imagine a trampoline (solid) vs. a pool of water (liquid). You can bounce in different directions on a trampoline, but you can only make splashes on the surface of the water!

• Inside devices like smartphones, a flexible material moves back and forth with the frequency of the sound.
• This movement creates high and low-pressure regions in the nearby air.
• These pressure regions then move as a longitudinal traveling wave.

Did you know? The waves decrease in amplitude (size) as they move further out because they spread and lose some energy as heat!

• π 2 rad = phase difference between compressions and corresponding displacement maxima.
• Maximum particle displacement is when the pressure is average.
• No particle displacement? Pressure is maximum difference from atmospheric pressure.
• Pressure goes up and down in one cycle.

Real-world Example: Think of it like a roller coaster. The top of a loop is max displacement, while the bottom is no displacement!