Physics 11 Vibrations and Waves Mr. Jean December 15 th, 2014

The plan: n Video Clip of the day oo oo n Introduction to waves n Ways to transmit & transfer energy n Wave interference

There are two ways to transmit information/energy in our universe: 1) Particle Motion 2) Wave Motion

Light and Sound Both are vibrations of energy and they share some similar wave properties.

Simple Harmonic Motion: n Any motion that repeats itself precisely over equal periods of time when generated by a linear restoring force in accordance to Hooke’s Law.

Piston Example:

2.WAVE DESCRIPTION Frequency ( f ) is the number of vibrations per unit of time made by the vibrating source. Units - cycles per second 1/s Hertz (Hz)

Picture of a Transverse Wave Crest Trough Wavelength A A - Amplitude

Distance between adjacent crests in a transverse wave. Distance a wave travels during one vibration. in meters Wavelength ( )

n The period (T) of a vibration is the time required to make one vibration. n The (T) of a wave is the time required to generate one wave. n The period (T) of a wave is the time required to generate one wave. n It is also the time required for the wave to travel one wavelength.

Frequency Period

In symbolic form or

Example Question: n A mass suspended from the end of a spring vibrates up and down 24 times in 36 seconds. What is the frequency and period of the vibration?

Example Question: n A mass suspended from the end of a spring vibrates up and down 24 times in 36 seconds. What is the frequency and period of the vibration?

Wave Characteristics: n e/physics/vibration-and- waves/wave-characteristics/ e/physics/vibration-and- waves/wave-characteristics/ e/physics/vibration-and- waves/wave-characteristics/

3.WAVE MOTION n n Energy is transported by particles or waves. n n A wave is a disturbance transmitted through a medium. n n Exception: light does not require a medium.

4.WAVE SPEED The average speed is defined as

For a wave, if the distance traveled is a wavelength ( ), then the time to travel this distance is the period (T). Then or

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 Machine

5.TRANSVERSE WAVES Demonstration: Transverse Waves Examples: string musical instruments ripples on water electromagnetic waves

6.LONGITUDINAL WAVES Video - 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 Waves SlideSlide - Interference Slide

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 n n 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. n Demo - Rope and strobe n Demo - Mechanical overhead model

n There is no vibration at a node. n n There is maximum vibration at an antinode.  is twice the distance between successive nodes or successive antinodes.