1. Ch 15 Waves

2. The Nature of Waves
Wave- Any disturbance that transmits energy through matter or empty space.
Wave Energy
Energy can be carried away from its source by a wave
Waves transfer energy – NOT MATTER.

3. Energy Transfer Through a Medium
Medium- a substance through which a wave can travel.
Can be a solid, liquid, or gas.
When a particle vibrates (moves back and forth) it can pass its energy to a particle next to it.

4. Some waves need a medium – others don’t
DON’T need a medium
Sound waves
Mechanical waves
Electromagnetic Waves
- Visible Light
- Microwaves
- X rays

5. Types of Waves
Transverse Waves- Waves in which the particles vibrate in an up-and-down motion.
Particles move across, or perpendicular to the direction the wave is going.
Crest- The highest point of a transverse wave.
Trough- The lowest point of a transverse wave (between 2 crests)

6. Transverse Waves

7. Types of Waves
Longitudinal Waves- The particles of the medium vibrate back and forth along the path the wave moves. Particles more parallel to the direction the wave is moving
Compression- A part of a longitudinal wave where the particles are crowded together.
Rarefaction-A part where the particles are spread apart.
Sound waves are longitudinal waves.

8. Longitudinal Wave

9. 1.2 Properties of Waves Amplitude – Height of a wave.
The larger the amplitude is, the taller the wave is.
The larger the amplitude is, the more energy the wave has

10. Properties of Waves
Wavelength- The distance between any two crests or compressions next to each other in a wave.
The shorter the wavelength the more energy the wave has.

11. Properties of Waves
Frequency- The number of waves produced in a given amount of time.
Expressed in Hertz (Hz)
1 Hz = 1/s
Higher frequency means higher energy

12. Properties of Waves Wave Speed: The speed at which the wave travels
V = λ x f
SI Units
Wave Speed ( v)
m/s
Frequency (f) Hz
Wavelength (λ) m

13. Frequency and Wavelength Relationship
Frequency and wavelength are inversely related.
An increase in frequency causes a decrease in wavelength
An increase in wavelength causes a decrease in frequency

14. Calculations
Determine the wave speed of a wave that has a wavelength of 5 m and a frequency of 4 Hz.

15. Calculations
What is the frequency of a wave if the wave has a speed of 12 m/s and a wavelength of 3 m?

16. Calculations
A wave has a frequency of 5 Hz and a speed of 18 m/s. What is the wavelength?

17. Wave Interactions Transmitted Waves
Refraction- The bending of a wave as the wave passes from one medium to another at an angle
Wave speed changes when a wave moves from one medium

18. Refraction of Different Colors
Dispersion- Light rays are spread out into separate colors.
Each color of light has it’s own wavelength.
Diffraction- The bending of waves around a barrier or through an opening that changes its direction

19. Wave Interactions
Interference- Waves occupy the same space at the same time.
Constructive Interference- the crest of one wave overlaps the crest of another wave.
The new amplitude of the combined wave is larger than the original waves
Destructive Interference- The crest of one wave overlaps with the trough of another wave.
The new amplitude of the combined wave is smaller than the original waves.

20. Constructive & Destructive Interference