1. Quiz Review – Mechanical Waves, Ocean Waves and Sound
April 19, 2018

2. A wave does two things A wave moves back and forth (oscillates)
Waves
A wave does two things
A wave moves back and forth (oscillates)
A wave transfers energy

3. Kinds of Waves There are three kinds of waves
Mechanical waves like ocean waves, slinky waves, earthquakes, and sound
Mechanical waves need a medium to travel through like water for ocean waves or air for sound
Electromagnetic waves like light
They don’t need a medium
Gravitational waves

4. Two Shapes of Mechanical Waves
If a mechanical wave oscillates in the same direction the energy is moving, it is a compression wave (it squeezes together), also called a longitudinal wave
If a mechanical wave oscillates perpendicularly to the energy, it is called a transverse wave

7. Parts of Waves Waves have four parts
The crest is the top of a transverse wave, or the squeezed part of a compression wave
The trough is the bottom of a transverse wave, or the spread apart section of a compression wave
The midline is a line that runs halfway between the crest and the trough
The nodes are where the wave and the midline meet.

8. Measuring Waves There are three ways you can measure waves
Frequency is the number of waves that pass in a second. 1 wave/second is called a hertz
Wavelength (λ) is how long a wave is. It is measured from crest to crest or trough to trough.
Amplitude is how high the wave goes. It is measured from midline to crest or midline to trough.

9. Relationships Between Wave Measurements
Frequency and Wavelength are inversely related. When one goes up, the other goes down by the same fraction.
Wavelength times frequency equals velocity (speed)

10. Waves and Energy
The energy of a wave is proportionally related to the square of the amplitude (more A=more E2)
The energy of a wave is proportionally related to the frequency. (more f =more E)
The energy of a wave is inversely related to the wavelength. (more λ = less E)

11. Sound Waves
Sound waves are caused by vibrations in matter (usually in the air)
As the air molecules vibrate, they are pressed together into pulses – which is a compression wave.
Air molecules push against new molecules in the air, making them vibrate
This happens until the vibrating air hits your eardrum

12. More About Sound
The amplitude of the wave controls the volume. More amplitude is a louder sound.
The frequency of the wave controls the pitch. Higher frequency (and shorter wavelength) waves make higher notes.

13. Engineering
When we engineer solutions to problems, we need to consider criteria and constraints.
A criterion is one of the things you need to do – in other words it’s how you’re solving your problem.
A constraint is a limitation. In other words, it’s what you can’t do.

14. The Engineering Cycle