Introduction to Waves and Wave Types

Waves and Sound

• The maximum displacement of the disturbance from the equilibrium position is called amplitude.
• The highest point in a wave is called a crest.
• The lowest point in a wave is called a trough.
• The length of the wave between two crests or two troughs is called the wavelength.

Types of Waves

• In a longitudinal wave, the medium oscillates parallel to the direction of the wave pulse.
• In a transverse wave, the medium oscillates perpendicular to the direction of the wave pulse.
• Compression is a region where the particles are close together.
• Rarefaction is a region where the particles are spread apart.

Examples of Waves

• An example of a longitudinal wave is a sound wave in a gas.
• An example of a transverse wave is a light wave.

Properties of Waves

• A period is the time taken by the wave to complete one oscillation.
• The symbol for period is T and its unit is seconds (s).
• The formula for period is T = 1/f, where f is the frequency.
• Sound is a form of mechanical wave that requires a medium to propagate.

Frequency

• Frequency is the number of oscillations or cycles per second.
• The symbol for frequency is f and its unit is Hertz (Hz).
• The formula for frequency is f = 1/T, where T is the period.

Longitudinal Wave Pattern

• In a longitudinal wave, the particles oscillate back and forth along the direction of propagation.

Pressure and Temperature

• High pressure is caused by the particles being compressed, and low pressure is caused by the particles being rarefied.
• In warmer temperatures, sound travels faster.

Echoes and Human Hearing

• An echo is a repeated sound that is reflected back to the listener.
• Humans can hear sound between 20 Hz and 20,000 Hz.

Pitch and Frequency

• Pitch is the perception of the frequency of a sound wave.
• Lower the pitch means higher the frequency.

Doppler Effect

• The Doppler effect occurs when there is relative motion between the source and the observer.
• As the source approaches, waves get shorter (λ decreases).
• As the source passes by, waves are stretched out (λ increases).
• The only thing that changes in the Doppler effect is the wavelength.

Speed of Sound and Mach Speed

• The speed of sound in liquid, gas, and solid (from slowest to fastest) is approximately 343 m/s, 1,482 m/s, and 5,960 m/s respectively.
• Mach speed is the speed of an object as a multiple of the speed of sound (M = v / v_sound).

Sonic Boom and Mach Cone

• A sonic boom is a shockwave produced when an object breaks the sound barrier.
• A mach cone is the cone-shaped shockwave produced by an object traveling at supersonic speeds.

Noise Cancellation and Infrasound/Ultrasound

• Noise cancellation works by producing a sound wave with the same amplitude but opposite phase to cancel out the noise.
• Infrasound is sound with frequencies below 20 Hz, while ultrasound is sound with frequencies above 20,000 Hz.