1. Chapter 14
Waves

2. Waves carry energy without transporting matter
a repeating disturbance or movement that transfers energy through matter or space
A rhythmic disturbance that carries energy through matter or space.
Molecules pass energy on to neighboring molecules
Waves carry energy without transporting matter
All waves are produced by something that vibrates
Medium - material which a wave travels thru
May be solid, liquid, or gas
Not all waves need a medium to travel through
Example: Light waves
Wave Pulse
A single bump or disturbance that travels through a medium

3. Longitudinal or Compressional waves
Mechanical waves
waves that can travel only through matter
Transverse waves
matter in the medium moves back and forth at right angles to the direction that the wave travels.
Example: Water waves
Longitudinal or Compressional waves
matter in the medium moves in the same direction that the wave travels.
Example: Sound waves
Surface Waves
Combination of both transverse or compressional
examples: water waves, seismic waves

4. Transverse waves have crests & troughs
Ways waves differ
1. How much energy they carry
2. How fast they travel
3. How they look
Transverse waves have crests & troughs
Crest —the highest points
Troughs—the lowest points.
Compressions
Dense regions of compressional waves
Rarefactions
Less dense regions of compressional waves

5. Wavelength (λ) Frequency (f)
the distance between one point in the wave and the nearest point just like it
Frequency (f)
how many wavelengths pass a fixed point each second
Expressed in hertz (Hz)
As frequency increases, wavelength decreases.
The frequency of a wave equals the rate of vibration of the source that creates it.

6. velocity = wavelength * frequency Speed of a wave = v = λ*f
Wave velocity, v
describes how fast wave moves forward
velocity = wavelength * frequency
Speed of a wave = v = λ*f
f = 1/T = 1/period
Light waves travel faster than sound waves
Sound waves travel faster in liquids and solids than in gas
Light waves travel faster in gases and empty space than in liquids & solids

7. Amplitude of transverse waves
a measure of the energy in a wave
More energy a wave carries, the greater its amplitude.
Amplitude of compressional waves is related to how tightly the medium is pushed together at the compression
The denser the compressions, the larger the amplitude is and the more energy the wave carries
The less dense the rarefactions, the larger the amplitude and the more energy the wave carries
Amplitude of transverse waves
The distance from the crest or trough of a wave to the normal position of the medium
Ex. how high ocean wave appears above water level

8. Reflection occurs when a wave strikes an object and bounces off of it.
All types of waves can be reflected.
The angle of incidence always equals the angle of reflection
Normal
An imaginary line that is perpendicular to reflective surface

9. Incidence Wave Angle of incidence Angle of reflection Refraction
The wave that strikes the boundary
Angle of incidence
the angle formed by the wave striking the surface and the normal
Angle of reflection
angle formed by reflected wave and normal
Refraction
bending of a wave caused by a change in its speed as it moves from 1 medium to another

10. The greater the change in speed is, the more the wave bends.
When a wave passes into a material that slows it down, the wave is bent toward the normal.
When a wave passes into a material that speeds it up, the wave is bent away from the normal.
Diffraction
an object causes a wave to change direction and bend around it
If obstacle is smaller than wavelength, wave diffracts a lot
If obstacle is larger than wavelength, wave does not diffract much
The larger the obstacle is compared to the wavelength, the less the waves will diffract

11. Constructive interference Destructive interference
ability of two or more waves to combine & form a new wave
Waves pass thru each other & continue in original direction
New wave exists only while original waves are overlapping
Constructive interference
waves add together
Destructive interference
waves subtract from each other

12. Standing waves Nodes Resonance a wave pattern that stays in one place
Form when waves of equal wavelength & amplitude that are traveling in opposite directions continuously interfere with each other
Nodes
the places where two waves always cancel each other
Resonance
ability of an object to vibrate by absorbing energy at its natural frequency