1. Waves
Ch – 25.4

2. Mechanical Waves Waves that travel only through matter
Require medium (matter): Solid, liquid or gas
Which of the following are mechanical waves?
Sound
Light
Ocean Waves
Seismic waves

3. Two types of mechanical waves
Transverse Waves
Matter in the medium moves back and forth at right angles to the direction that the wave travels
Example: ocean waves
Compressional (Longitudinal)Waves
Matter in the medium moves back and forth along the same direction that the wave travels
Example: coiled spring toys and sound waves

4. A sine curve is a pictorial representation of a wave

5. Parts of a Wave Transverse waves Compressional Waves
Crest- highest point of the wave
Trough- lowest point
Compressional Waves
Compressions: regions where waves are crowded close together
Rarefaction: regions where waves are less dense

6. Wavelength
Distance between one point on a wave and the nearest point just like it
Crest  crest
Trough trough
Compression  compression
Rarefaction  rarefaction

7. Practice Questions: Which graph has the longer wavelength?
Graph A
Which graph has the greater frequency?
Graph B
What is the relationship between wavelength and frequency?
Inversely proportional A B

8. Wave Speed Depends on: Type of wave Temperature of material
Sound waves travel faster through solids and liquids
Light waves travel faster through space
Temperature of material
Higher temperatures, higher speeds

9. Calculating Wave Speed
V (speed in m/s) = f(frequency in Hz) x λ(wavelength in m)

10. Practice Calculation 2
What is the speed of a sound wave that has a wavelength of 2.00 m and a frequency of Hz? V= f λ = * 2 = 341 m/s

11. Amplitude and Energy
Amplitude (intensity) is directly proportional to the energy of the wave
Transverse: distance from midpoint to crest or trough
Compressional: how tightly the medium is pushed together at compressions