1. Notes on Chapter 25 Vibrations & Waves
Conceptual Physics
Notes on Chapter 25
Vibrations & Waves

2. Wave Vibration Vibrations & Waves Any “wiggle” in time is called a
Make that “wiggle” move through space, it makes a
Wave

3. Vibrations & Waves
The time is takes for a vibration to make a back-and-forth swing is called the Period of the wave.
A long pendulum has a longer period than a shorter pendulum; that is, it swings back-and -forth more slowly --- less frequently --- than a short pendulum.

4. Simple harmonic motion.
Vibrations & Waves
To produce this “wiggle”, you can use a spring, a pendulum, or string. Any of these will produce
Simple harmonic motion.

5. Vibrations & Waves
Let’s look at a wave: A
C D B

6. Vibrations & Waves High points on the wave are called Crests.
Low points on the wave are called Troughs.
The Wavelength is the distance from the top of one crest to the top of the next crest, or distance between successive identical parts of the wave.
Amplitude refers to the distance from midpoint to crest (or trough) on a wave.

7. Vibrations & Waves
Frequency is how often a wave passes a given point in a given time. (A complete back-and-forth swing, or up-and down movement.)
Frequency is measured in cycles per second or
Hertz (Hz).

8. Vibrations & Waves Example:
1 cycles per second is 1 Hz.
2 cycles per second is 2 Hz.
Higher frequencies : kHz Hz
MHz Hz
NOTE FROM ABOVE that frequency and period are related:
Frequency = 1 / period
Period = 1 / frequency
They are inverses of each other!

9. Transverse Wave Vibrations & Waves
A wave that is traveling at right angles to the direction of travel.
“Shaking the rope up and down”

10. Longitudinal Wave Vibrations & Waves
A wave that is traveling in the same direction to the direction of travel.
“Push in and pull out”

11. Vibrations & Waves Interference
Interference can be
CONSTRUCTIVE or
DESTRUCTIVE.

12. Vibrations & Waves
Constructive interference is when two waves in phase add to make a larger wave.
Destructive interference is when two waves out of phase subtract to make a smaller wave.

13. Vibrations & Waves Standing Waves
A standing wave occurs when a wave is reflected back toward the source.

14. Vibrations & Waves
In a standing wave, certain parts of the rope remain stationary --- NODES.
The largest amplitudes are known as ---ANTINODES.

15. Vibrations & Waves Doppler Effect
A change in frequency due to the motion of the object or observer.
The Doppler Effect can also be observed in light --- blue or red shift!