Physics 11

Chapter #8 Vibrations and Waves

Mr. JeanMay 28th, 2012

The plan:

Video Clip of the dayVideo Clip of the day Science Fair PresentationsScience Fair Presentations Introduction to waves Introduction to waves Ways to transmit & transfer energyWays to transmit & transfer energy Wave interferenceWave interference

Science Fair:

CherCher Abby’s GroupAbby’s Group

In symbolic form

T 1foror

T1f

Example Question: A mass suspended from the end of a spring A mass suspended from the end of a spring

vibrates up and down 24 times in 36 vibrates up and down 24 times in 36 seconds. What is the frequency and period seconds. What is the frequency and period of the vibration? of the vibration?

Example Question: A mass suspended from the end of a spring A mass suspended from the end of a spring

vibrates up and down 24 times in 36 vibrates up and down 24 times in 36 seconds. What is the frequency and period seconds. What is the frequency and period of the vibration? of the vibration?

Wave Characteristics:

http://www.brightstorm.com/scienchttp://www.brightstorm.com/science/physics/vibration-and-waves/wave/physics/vibration-and-waves/wave-characteristics/e-characteristics/

3. WAVE MOTION

Energy is transported by particles or waves.

A wave is a disturbance transmitted through

a medium.

Exception: light does not require a medium.

4. WAVE SPEED

The average speed is defined asThe average speed is defined as

time

distancev

For a wave, if the distance traveled is a For a wave, if the distance traveled is a

wavelengthwavelength ( (), then the time to travel this ), then the time to travel this

distance is the distance is the periodperiod (T). Then (T). Then

Tv

fv oror

is true for all waves.

Note: v is dictated by the medium.

(must change medium to change v)

f is dictated by the source.

(must change the source to change f )

Demo - Complete Bell Wave MachineDemo - Complete Bell Wave Machine

fv

5. TRANSVERSE WAVES

Demonstration: Transverse WavesDemonstration: Transverse Waves

Examples: string musical instruments

ripples on water

electromagnetic waves

6. LONGITUDINAL WAVES

Video - Slinky Longitudinal WavesVideo - Slinky Longitudinal Waves

Parameters

Rarefactions are regions of low density.

Compressions (condensations) are regions of high density.

is the distance between successive rarefactions or successive compressions.

7. INTERFERENCE

Video - Superposition of WavesVideo - Superposition of Waves

SlideSlide - Interference - Interference

Constructive interference occurs when waves are in phase, that is when crests are superimposed and troughs are superimposed.

Destructive interference occurs when waves are out of phase, that is when crests are superimposed with troughs.

Interference is a characteristic of all waves.

Demonstrations with Audacity

Standing Waves

When two sets of waves of equal amplitude and wavelength pass through each other in opposite directions, it is possible to create an interference pattern that looks like a wave that is “standing still.” It is a changing interference pattern.

Demo - Rope and strobeDemo - Rope and strobe Demo - Mechanical overhead modelDemo - Mechanical overhead model

There is no vibration at a node. There is maximum vibration at an antinode. is twice the distance between successive

nodes or successive antinodes.