1. Waves

2. Vibrations and Waves
The source of all wave motion is a disturbance or vibration.
Waves transmit energy, not matter.

3. Transverse Waves Longitudinal Waves Modeled by using a sine wave.
Types include Electromagnetic waves and ocean waves.
Depending on the type of wave, transverse waves may or may not require a medium.
Modeled by using a spring.
Sound waves are longitudinal waves.
Longitudinal waves are mechanical waves – they require a medium.
compression
rarefaction

4. Types of Waves
A transverse wave has oscillations perpendicular to the direction the wave moves.
A longitudinal wave has oscillations in the same direction (parallel) as the wave moves.

5. Period and Frequency
Period is the time needed for a wave to make one complete cycle (wavelength) of motion.
(T) Unit: seconds
Frequency is the number of cycles (wavelengths) per unit time.
(f) Unit: hertz (Hz)
Period and frequency are inverses.

6. Wave Speed, v Speed of wave (v) depends upon:
Medium
Frequency, f
Wavelength, λ
Wave Speed = wavelength x frequency
v = λ f
Freight car analogy-- each car is 5 meters long (wavelength), and 2 cars cross the road each second (frequency). Speed of train = 10 m/s (speed = Distance / time!!)
NOTE: If speed of waves are constant (say for sound or light) then wavelength (λ) and frequency (f) are inversely related.

7. A B C

8. Wave Interactions

9. Interference
When two or more waves are at the same place at the same time, the resulting effect is called interference.
Constructive interference - when the crest of one wave overlaps the crest of another, their individual effects add together. The result is a wave of increased amplitude.

10. Wave Interactions – Interference
Destructive interference – when the crest of one wave overlaps the trough of another, their individual effects are reduced. The result is a wave of decreased amplitude.

11. Standing Waves
result of interference of two waves traveling at the same frequency, amplitude and wavelength but in opposite directions.
the nodes remain stationary. This is where you can touch a standing wave on a rope without disturbing the wave.
The positions with the largest amplitudes are know as antinodes. Antinodes occur halfway between nodes.
Standing waves can be set up on the strings of musical instruments, in organ pipes, and by blowing across the top of a soda bottle.

12. Standing Waves λn = 2L/n Wavelength, l
l1 = 2L
l2 = 2L/2 or L
l3 = 2L/3
l4 = 2L/4 or ½ L
Only certain frequencies of vibration produce standing waves for a given string length.
The wavelength of each of the standing waves depends on the string length, L, and the number of nodes, n.
λn = 2L/n

13. Wave Interactions – Reflection

14. Wave Interactions – Diffraction

15. Wave Interactions – Refraction

16. A certain FM radio stations broadcasts at a frequency of 9.45 x 107 Hz. These radio waves travel at a speed of 3.00 x 108 m/s. What is the wavelength of these radio waves?

17. A drum is struck, producing a wavelength of 110 cm and a speed of 2
A drum is struck, producing a wavelength of 110 cm and a speed of 2.42 x 104 m/s. A. What is the frequency of the wave? B. What is the period?

18. A wave with a frequency of 60
A wave with a frequency of 60.0 Hz travels through a piece of plastic with a wavelength of 134 cm. What is the speed of this wave?

19. Standing Waves
Although waves usually travel, it is possible to make a wave stay in one place. A wave that is trapped in one spot is called a standing wave.
Standing waves are the result of interference. The resultant wave is created by the interference of two waves traveling at the same frequency, amplitude and wavelength but in opposite directions.

20. Standing Waves
In a standing wave, the nodes remain stationary. This is where you can touch a standing wave on a rope without disturbing the wave.
The positions on a standing wave with the largest amplitudes are know as antinodes. Antinodes occur halfway between nodes.
Standing waves can be set up on the strings of musical instruments, in organ pipes, and by blowing across the top of a soda bottle.

21. Standing Waves λn = 2L/n Wavelength, l
l1 = 2L
l2 = 2L/2 or L
l3 = 2L/3
l4 = 2L/4 or ½ L
Only certain frequencies of vibration produce standing waves for a given string length.
The wavelength of each of the standing waves depends on the string length, L, and the number of nodes, n.
λn = 2L/n