1. Mechanical Waves

2. What are waves?
Wave – a disturbance that transfers energy from place to place.
Medium – the material thru which a wave passes
Waves travel trough the medium without actually moving the medium with it.

3. Two Categories of Waves
Mechanical
These are waves that transfer energy through matter
They require a medium (Solid, liquid, or gas)
Examples of Mechanical Waves:
Transverse and Longitudinal waves
Electromagnetic
These are waves that transfer energy through a field
They do NOT require a substance to travel through
Examples of Electromagnetic Waves: Microwaves and Cellular Phones

4. Types of Mechanical Waves:
• Transverse Waves: waves that move the medium at
right angles to the direction in which the waves are
traveling.
• Longitudinal Waves: move particles parallel to the
direction the wave is moving, “push-pull” waves.

5. Wave Particle Movement
Waves travel trough the medium without actually moving the medium with it. Basically the medium stays put while the wave moves some distance.

6. How do we know waves carry energy and not matter?
Think about an earthquake.
When seismic waves travel through an area, the ground shakes from side to side and up and down, but the ground itself does not travel over a distance.
Only the ENERGY moves!

7. Properties of Waves
• Amplitude – in a transverse wave – the height away from the “rest” position. The amplitude in a longitudinal wave is the measure of how compressed or rarefied the medium becomes.
• Wavelength – the distance between two corresponding parts of a wave.
• Frequency – the number of complete waves that pass a given point in a certain period of time. Frequency is measured in HERTZ, one Hz is a wave that occurs once
every second.

8. So what makes a wave?

9. Longitudinal waves create points called compressions and rarefactions.
Compressions: parts where the coils are close together
Rarefactions: parts where the coils are spread out

10. What causes waves? You MUST have energy.
Mechanical waves are produced when a source of energy causes a medium to vibrate.
A vibration is a repeated back-and-forth or up-and- down motion.
When a vibration moves through a medium, a wave results.

11. Examples

12. How do we calculate WAVE SPEED?

13. Waves can also be reflective and refractive
Waves can bounce off of something after striking it. That is a reflection. Sound and light waves can equally be reflective in nature and bounce energy wave back with equal force.
Example) screaming in a canyon
There are also times waves can not bounce back. Waves can bend at a different angle and refract. This occurs when wave energy is travel at a different speed than the medium.

15. Interactions of Waves • Diffraction – Wave passing a barrier or going
through a hole in a barrier bends and causes the
wave to wrap around the barrier.

17. Vocabulary Medium Wave Reflection Refraction Amplitude Compression
Crest
Longitudinal
Rarefaction
Transverse
Trough
Wavelength
Frequency
Mechanical