waves and sound - schools.misd.orgschools.misd.org/page/download/11856/0/shm waves student.pdf ·...
TRANSCRIPT
WAVES and Simple
Harmonic Motion
Add these words to the ovals in your
vocabulary frayer card packet
Vocab Quiz Tuesday 2/28
Packet due Monday 3/6amplitude
compressions
crest
diffraction
energy
frequency
interference
longitudinal
mechanical
medium
period
reflection
refraction
superposition
transverse
trough
wave
wavelength
Wave
A repeating and periodic disturbance that transfers energy from one place to another
WAVES TRANSPORT ENERGY NOT MATTER!!!
The particles in a wave vibrate however they do NOT move along with the wave, only the wave front itself moves on.
Pulse
a single non repeated disturbance
Mechanical Waves
Medium required to transfer energy
can be transmitted through solids, liquids, and gases.
they can not travel through space
Examples:
sound waves
water waves
Electromagnetic Waves
Medium NOT required to transfer energy
are able to transmit energy through a vacuum as well as solids, liquids, and gases.
They can travel through space
Examples: cosmic, gamma, x-ray, ultraviolet, visible light, infrared, microwave, radio (All waves on the EM Spectrum)
Types of Waves
Transverse
Compressional (Longitudinal)
Transverse Wave Diagrams
Transverse Wave Motion
Transverse Waves
Vibration is perpendicular (up & down)
to the direction the wave is moving. ex. light waves, snakey
Direction of Wave
Motion of Molecules
Longitudinal (compression)
Rarefaction
Compression Wavelength
Longitudinal Waves: Anatomy
Rarefaction: region in which the particles are spread out
Compression: region in which the particles are close together
A wavelength: composed of a complete rarefaction and a complete compression.
Longitudinal Wave Motion
Longitudinal (Compressional) Waves
vibration is parallel to the direction of
the wave. These waves require a
medium (such as air or water)
through which to travel.
ex. Sound waves (looks like a spring)
Direction of Wave
Direction of Movement
Calculating Wave Speed:
v = f
Where
v = wave speed in m/s
f = frequency in Hz
= the wavelength in meters.
Which wave has the longest
wavelength?
Which wave has the greatest
frequency?
What is the relationship between f and
λ when velocity held constant?
inversely related
IMPORTANT
The speed of the wave however depends solely on the medium through which a wave is traveling
Velocity of a Wave
The equation v=d/t can also be applied.
Energy and Amplitude
The rate at which energy is transferred by a wave depends on the _________ of the wave.
Energy of a wave IS NOT related to the speed of the wave.
amplitude
Which wave has greatest
amplitude?
Reflection
Reflection is the bouncing back of a wave at a boundary.
Examples of Reflection
Mirrors
Surface of water
A reflected sound wave is called an echo.
Refraction
Refraction is the change in speedof a wave at a boundary as it passes from one medium to another.
the wave “bends” or changes direction.
The speed changes however the frequency stays the same.
This means that the wavelength must change.
For refraction to occur,
Causing the wave to change speed & direction
The wave must enter a new medium (at an oblique angle).
Examples
Fish tanksWindows
Diffractionthe spreading of a
wavearound a barrier orthrough an opening.
The medium does not change!!!!!
In order for diffraction to occur, the opening or edge must be much smaller than the incident wave
These images are created by a ripple tank
Diffreaction Applications
Holograms (Not just depth, in it)
Flashlights
Waves at the marina
Double Slit Diffraction
Results in constructive and destructive interference
Interference
the result of the superposition of two or more waves, i.e. two or more waves occupy the same place at the same time.
constructive vs. destructive interference
Interference can be either constructive (build) or destructive (cancel).
Depends on how the waves overlap
Constructive interference
•waves align in sync or in phase
•displacement is in same direction
•Resultant wave has greater
amplitude than orignal waves
.
Destructive interference
•waves are out of sync(out of phase)
•displacement is in opposite direction
•Resultant wave has smaller amplitude than
orignal waves
•Total destruction if waves of equal amplitudes
meet 180O out of phase
node vs antinode
node: a point in a medium that is completely undisturbed when a wave passes.
Antinode: the point of maximum displacement; it can be either a crest or a trough
Standing Wave: A result of
interference
Created when two periodic waves of equal amplitude and wavelength travel in the opposite direction.
the nodes and antinodes of a wave are in a constant position.
as the frequency of the wave increases, the number of nodes and antinodes increases in the same amount of space.
Frequency and Period
T is period in seconds; time for one cycle to occur
f is frequency in Hz; how often one wave passes per second
f = # of occurrences T = time (sec)
time (sec) # of occurrences
Frequency and period are inversely related.
T=1/f f = 1/T
Periodic Motion
When a vibration or oscillation repeats itself over the same path
A specific form of periodic motion in which the restoring force is proportional to distance from the equilibrium position.
Simple _________ Motion (SHM):Harmonic
Objects that exhibit SHM
Spring Systems*
Pendulums*
Circular Motion
Waves
Sound, Light, Pressure
Period on a Spring
If we stretch a spring with a mass and release it, it will oscillate.
This is SHM!
What is the period of this
Motion?
Horizontal Springs
It has a mass of some kind attached to a spring.
This spring is stretched and released. This causes the entire system to oscillate. (move back and forth)
Hooke’s Law (force of a spring)
Fspring: magnitude of the distorting or restoring force in Newtons
K: spring constant or force constant (stiffness of a spring) in Newtons per meter (N/m)
x: displacement from equilibrium in meters
kxFS
If time
Simple harmonic motion - Physics Flash Animations
Period on a Spring
The period of a spring system is given by the equation below:
T – the period of motion
m – Mass of the body attached
k – spring constant
k
mTs 2
Period
What is the relationship between mass and period of a spring?
What is the relationship between spring strength (Think spring constant) and period of a spring?
Remember that period is always in seconds!
What is the difference between period and frequency?
Formulas
Calculating Period and Frequency
ond
cyclesf
cycles
ondsT
sec
sec
T = period or time for one revolution or cycle (sec)
f = number of revolutions or cycles per second (Hz or sec-1)
Let’s take a jump!
http://departments.weber.edu/physics/amiri/director/DCRfiles/Energy/bungee4s.dcr
https://www.youtube.com/watch?v=_iXlef9GFTY
Out of chaos, comes order. The scientific explanation notwithstanding , this is some neat stuff to watch
Harvard built a device with a series of fifteen pendulums in a row, each one of them slightly longer than its neighbor.
The pendulums were set into motion and the result was captured on video. The patterns that appear in this short video are fascinating to watch and to think about. Prepare to be captivated by this simple device !
Click on the below link but before starting the video, READ the complete explanation.Fascinating. I want one !
http://sciencedemonstrations.fas.harvard.edu/icb/icb.do?keyword=k16940&pageid=icb.page80863&pageContentId=icb.pagecontent341734&state=maximize&view=view.do&viewParam_name=indepth.html#a_icb_pagecontent341734
The Pendulum Formula
T = period (s)
l = length (m)
g = acceleration due to gravity (m/s2)
g
lTp 2
pendulum wave appletvibrating spring wave applet