Waves for Dummy's
- Waves have a crest (top point), a trough (bottom point), and a midline (middle point).
- The amplitude is the amount of displacement or the distance from the midline to either the crest or trough.
- The period is how many seconds it takes for a wave to go through.
- The frequency is the amount of waves that occur in one second (measured in Hertz).
- Wavelength is the distance from crest to crest or the distance of one wave cycle.
- The amount of energy is determined by the waves amplitude.
What is a wave?
Waves
- A disturbance that transfers energy through matter or space
- A wave that needs a medium to travel through
- Examples - Sound waves, ocean waves, earthquake waves etc...
- Does not need a medium to travel through like light waves.
- When the oscillation is parallel to the direction of motion
- AKA... Side to side like a slinky
- When the oscillation is perpendicular to the direction of motion.
- AKA... up and down like a sin or cos wave.
Wave Speed
- Waves travel at a constant speed (no acceleration)
- Not effected by anything other than the medium it travels through.
Medium Boundaries
- Medium boundaries are the edges of the waves medium
- Open-Open ending has an anti-node on both sides
- Closed-Closed ending has a node on both sides
- Open-Closed ending has one anti-node on a side and one node on the other side.
The Dopler Effect
- The dopler effect is why you here a sound getting louder as it gets closer to you.
- All waves, electromagnet and mechanical, have the dopler effect.
- The dopler effect is only for moving objects.
- As an object is moving towards you the frequency increases which is why you hear a change in pitch (gets louder).
Wave Interference
- When waves interact with each other they can build each other up or tear each other down.
- Waves move through each other not bounce off one another like solid objects.
- Waves add or subtract from each other.
- Waves can be standing waves (look like they aren't moving are carrying energy).
- There can be total destructive or total constructive interference on waves.
- When waves have different frequency's you can hear the beat.
- Beat = |Frequency1 - Frequency2|
Source for the image above - Tyler Dunn's notebook
Standing Waves
- Standing waves are reflecting of the medium boundaries and interfering with each other so thats they appear to be standing.
- Standing waves have nodes and anti-nodes.
- Fundamental frequency is the simplest possible frequency where the wave is in the first harmonic.
- The standing wave equation is determined by the square root of the tension divided by the linear mass density.
Harmonics
- Waves have nodes and anti-nodes.
- Total destructive interference
- No energy on nodes (hold your finger on the node and it won't effect the wave)
- A closed end on a wave is a node
- Total constructive interference
- Most energy part of the wave
- An open end on a wave is a anti-node
- Waves can be in different harmonics (first, second, third, fourth, fifth, sixth, etc...)
- For the first harmonic the wavelength equal 1/2 the length of the string.
- The second harmonic the wavelength equals the length.
Videos
|
|