Learning Objectives

• Define a mechanical wave and how it transfers energy through a medium.

• Compare the three types of mechanical waves: transverse, longitudinal, and surface waves.

• Describe the key properties of a wave, including amplitude, wavelength, and frequency.

• Explain wave behaviors such as interference and the Doppler effect.

Key Vocabulary

Mechanical Wave

A disturbance in matter that transfers energy through it without moving the matter itself.

Medium

The matter a wave travels through. It can be a solid, liquid, or gas.

Transverse Wave

A wave where particles vibrate perpendicular to the direction the wave is moving.

Longitudinal Wave

A wave where particles vibrate parallel to the direction the wave is traveling.

Wavelength

The distance between two identical points on successive waves, like from one crest to the next.

Interference

This occurs when two waves meet and combine to create a new, temporary wave.

What is a Mechanical Wave?

• A mechanical wave is a disturbance that transfers energy through matter.

• ​The matter a wave travels through is called the medium.

• It needs a medium, so it cannot travel through a vacuum.

• Particles of the medium vibrate, but only the energy travels forward.

Types of Mechanical Waves

Transverse Wave

• Particles vibrate up and down, perpendicular to the wave's direction.

• These waves have high points called crests and low points called troughs.

• An example is creating a wave by shaking a piece of rope.

Longitudinal Wave

• Particles vibrate back and forth, parallel to the wave's travel direction.

• They have compressions and rarefactions where particles are pushed together or spread apart.

• Sound is a primary example of a longitudinal wave.

Surface Wave

• These combine both transverse and longitudinal wave motions.

• They occur at the surface between two different media.

• Particles move in a circular motion, like waves on water.

Properties and Equations of Waves

Wave Behaviors

Interference

• Two waves meeting while traveling through the same medium cause interference.

• Constructive interference creates a larger wave when two crests align together.

• Destructive interference is when a crest meets a trough, canceling each other.

Resonance

• Every object possesses its own unique natural frequency of vibration.

• Resonance happens when a force matches an object's natural frequency.

• This causes a dramatic increase in the amplitude of the vibrations.

Doppler Effect

• This is the apparent change in a wave's frequency during motion.

• It is due to motion between the wave source and an observer.

• A siren sounds higher as it approaches and lower as it moves away.

Common Misconceptions

Summary