Mechanical Waves

What is a mechanical wave?

• A disturbance in matter that carries energy from one place to another.

• Require a material to pass through called a medium.

• A medium can be a solid, liquid, or a gas.

• 3 types of mechanical waves.– 1. Transverse waves– 2. Longitudinal waves– 3. Surface waves

Transverse waves

• Cause the medium to vibrate at right angles to the direction of wave motion.

Wave motion Slinky motion

Parts of a transverse wave

• Rest position

wavelength

wavelength

node

• Crest – the top of a wave.

• Trough – the bottom of a wave.

• Wavelength – the distance from crest to crest or trough to trough.

• Node – where the wave intersects the rest position.

• Amplitude – distance from the rest position to a crest or trough – measures energy.

• Frequency – how many times the wave cycles in a given time period.– Usually measured in Hertz (Hz) – cycles per second– Low frequency– High frequency

Wavelength and Frequency

• These 2 are related

• As one increases, the other decreases.– Low frequency, large wavelength– High frequency, small wavelength

Longitudinal Waves

• Compression waves

• Move the medium the same direction as the wave.

• Made from compressions and rarefactions

Wave motionSlinky motion

Surface Waves

• Travel along the surface separating 2 media.– Ocean waves travel between water and air

• Have characteristics of both longitudinal and transverse waves.– Transverse part causes up and down motion.– Longitudinal part causes back and forth motion.

Wave Speed

• Speed = frequency X wavelength

• f

speed (m/s)

f = frequency (Hz)

wavelength (m)