1. Aim: What properties define wave classes?
HW: Problem Set

2. Review
Last time we talked about two kinds of waves and looked at the electromagnetic spectrum…
Describe the two types of waves?
On the EM spectrum, how does the frequency and wavelength vary across the spectrum?
How do you draw a wave?

3. Two Classes of Waves Transverse Waves Longitudinal Waves
The particles vibrate in a direction that is perpendicular to the waves propagation (direction of travel)
The particles vibrate in a direction that is parallel to the waves propagation

4. Direction of wave travel is PERPENDICULAR to the motion of the medium
Transverse Waves
Direction of wave travel is PERPENDICULAR
to the motion of the medium
Particles: ↕
Energy: ↔
Example:
Light Waves

5. Transverse Waves WAVELENGTH – the distance from one crest to another
AMPLITUDE – the amount that a wave rises or falls
Tells how much ENERGY the wave contains
CREST OR PEAK – the highest point on a wave
TROUGH – the lowest point on a wave

6. Direction of wave travel is PARALLEL to the
Longitudinal Waves
Direction of wave travel is PARALLEL to the
motion of the medium
Particles: ↔
Energy: ↔
Example:
Sound waves
Speed of Sound: 3.31 x 102 m/s

7. Longitudinal Waves WAVELENGTH – the distance from one compression to
another
COMPRESSION – area where particles in the medium
are densely populated
RAREFACTION – area where particles in the medium
are sparsely populated
AMPLITUDE – the size of a compression
The ENERGY contained in the wave

8. Envelope Activity
There are two situations regarding waves. Answer all the questions with your group.

9. 1. The frequency of a sound wave from a pipe organ is 264 Hz
1. The frequency of a sound wave from a pipe organ is 264 Hz. List and draw everything about this wave (speed, wavelength, wave type, class). 2. A light wave with a wavelength of 619 nm travels across the classroom. List and draw everything about this wave (Speed, frequency, wave type, class, COLOR). 3. Sound waves are longitudinal waves. Why is the sound from a speaker louder when you sit closer to it? (In other words has more energy).

10. Question 3
Sound waves are longitudinal waves. Why is the sound from a speaker louder when you sit closer to it? (In other words has more energy).
Because the amplitude of the sound wave gets smaller
the farther it gets from its source. Sitting closer
delivers more energy because the amplitude of the
sound wave is greater!

11. Wave Transmission Transverse Waves (Light) Longitudinal Waves (Sound)
DO NOT REQUIRE A MEDIUM
Sparse to Dense (air to water) – SLOW DOWN
Dense to Sparse (water to air) – SPEED UP
Longitudinal Waves (Sound)
MUST HAVE A MEDIUM
Sparse to Dense – SPEED UP
Dense to Spare – SLOW DOWN

12. Phase
To be IN PHASE, two points on a wave must be traveling in the same DIRECTION and have the same DISPLACEMENT from EQUILIBRIUM
“In Phase” = 0° or 360°
“Out of Phase” = 180°
Which points are in phase?

13. Phase The relative position between…
Two similar points on different waves
Pick the same point on each wave and look at the difference between their relative positions
360o out of phase, AKA IN PHASE 1 full wavelength apart
180o out of phase, 1/2 wave apart
90o out of phase, 1/4 wave apart
270o out of phase, 3/4 wave apart

14. Fundamentals Review
Answer the following questions regarding wave fundamentals with either a written response or calculation.

15. Fundamental 1
A sound wave travels from air into metal, then from metal into water. What happens to the speed of the wave?
Speeds up when going from air to metal.
Slows down when going from metal to water.

16. Fundamental 2
Determine the frequency of a wave with a wavelength of 500 meters if it travels at a velocity of 25 meters per second.
What is its period?
v = fλ
25 m/s = f (500 m)
f = 0.05 Hz
T = 1 / f
T = 1 / 0.05 Hz
T = 20 s

17. Summary
What is the difference between longitudinal and transverse waves?
What is an example of both transverse and longitudinal waves?
When does light slow down?
When does sound speed up?