1. Waves!

2. I. A little vocab… WAVE: MEDIUM:
A periodic disturbance in a solid, liquid or gas
MEDIUM:
Matter or space through which waves travel

3. II. Types of waves Waves can be classified by what they move through
Mechanical- Requires a medium
b. Electromagnetic-Does
not require a medium
Ex- light waves, radio waves, ultraviolet waves…

4. 2. Waves can also be classified by how they move
a. Transverse waves – travel perpendicular to the direction of the wave

5. b. Longitudinal waves (aka compression waves )
travel parallel to the direction of the wave

6. Surface Waves: Have BOTH
Occur at the border between two mediums…
Water waves: Particles at the surface move parallel and perpendicular (in circles)
The ball up and down and side to side

7. Draw your pictures

8. Waves Carry Energy
Simple Harmonic Motion- When you pull on a single spring, its mass continues to bounce up and down.
When pulled down, spring gains PE (elastic) As it moves back up when released, PE is transferred to KE
Mass goes past the original starting position
Back at the top, all energy is transferred to PE (gravitational & elastic PE)
When it moves down again, energy transfers back to KE and it keeps going

9. Damped Harmonic Motion- a vibration that fades out as energy is transferred from one object to another
When pulled down, the spring gains PE
Again, it will be converted to KE when released
BUT instead of that KE staying in that spring, it is transferred to the next spring in the line.

10. Anatomy of a Transverse Wave Crest: Trough:

11. Anatomy of a Longitudinal Wave Compression: Rarefaction:

12. Inquiry Lesson

13. How do we describe waves?
Wavelength
Amplitude
Period
Frequency

14. Wavelength () The distance between two identical parts of a wave
The distance btwn 2 crests for a TRANSVERSE wave or two compressions for a LONGITUDINAL wave.
The symbol for wavelenths is ____

15. Draw 2 waves – one with a long wavelength and one with a short wavelength!

16. Amplitude Distance from the middle of the wave to the crest
(or half the distance between the crest and the trough)
Larger waves have larger amplitudes and carry more energy
Sound Energy: The more amps the sound has, the ________________ it will be.
(usually represented by the line denisty for a compressional wave)
Low amplitude  Medium Amplitude HIGH Amplitude

17. Draw 2 waves – one with an amplitude of 5 mm and one with an amplitude of 2 mm

18. Period
The time required for 1 full wavelength of a wave to pass a certain point
Or the time required to complete one vibration of a particle in a medium
Represented by “t” (seconds)

19. Frequency The number of cycles/wavelengths/vibrations per unit of time
Represented by “f” ; f= 1/t
Measured in Hertz (named after Heinrich Hertz – 1888 – 1st demonstrated the presence of electromagnetic waves)
Equal to vibrations per second (1Hz = 1 vibration/1 second)
You can hear 20 Hz to 20,000 Hz
More vibrations = shorter amount of time for each

20. 1. Draw a wave with a period of .5 seconds and a frequency of 2 Hz

21. 2. Draw 2 waves – one with a high frequency and one with a low frequency:

22. Frequency of Light Spectrum (example)
Wide range of frequencies and wavelengths
Your eyes can detect 4.3 x 1014 Hz to 7.5 x 1014 Hz (visible light range)
Electromagnetic waves exist at frequencies we can’t see

24. Remember that each wave carries energy…
Higher frequency = more energy and shorter wavelength…The more wavelengths per unit time, the more energy.

25. Ex- sound waves…
Sound waves – travel as spherical waves from a speaker
Wave front – each circular wave
As they travel out, the wave front gets bigger – each front has the same amount of energy. As the wave front gets bigger, the energy is spread out over a bigger area (so that is why these waves are damaging close-up –close to speaker or close to light)

26. Wave speed – how fast a wave moves
Speed = wavelength / period
So…
Wave speed = frequency x wavelength (because the period is the inverse of the frequency

27. Wave speed depends on medium
Sound waves can travel in air
However, they travel even faster in solids than in air or water
Example: hitting a metal railing and listening (you will hear two bangs)
Why?
The first sound comes through the steel rail itself and reaches you shortly before the second sound, which travels through the air.

28. Wave speed depends on medium
In a gas, particles are farther apart so it takes longer for them to find each other and bump into each other - sending the wave
In liquids, particles are closer together so waves travel faster
In solids, particles are very close together so waves travel the fastest

29. Example: Earthquakes (you don’t need to know this…yet)
Produce seismic waves
P waves (primary) – travel faster, arrive first, longitudinal waves (shake everything side-to-side)
S waves (secondary) – slower, carry more energy, transverse waves (shake everything up and down – more damage)

31. 10. Doppler Effect First – pitch is determined by frequency
Sound waves travel out from an object in wave fronts and hit your eardrum (when they hit your eardrum, they have a frequency equal to the number of wave fronts that hit your ear
Ambulance example:
When the ambulance moves toward you, the sound waves are compressed because the ambulance moves a short distance – so the waves hit your eardrum at a higher frequency – higher pitch
Then, when the ambulance moves away from you, the distance between the wave fronts is more than before, so the frequency is lower – pitch is lower
Doppler effect can also happen in light and other types of waves

32.
wave speed different medium
surface wave
transverse right angles
reflection