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Vocabulary you’ll need …. A Wave is a disturbance that propagates through a material medium or space . Waves transfer energy without the bulk transport of matter. Types of Waves. Waves are classified by 1) The use of a medium or not to carry the energy - PowerPoint PPT Presentation
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Vocabulary you’ll need …
A Wave is a disturbance that propagates through a material medium or space.
Waves transfer energy without the bulk transport of matter.
Types of Waves
Waves are classified by
1) The use of a medium or not to carry the energy
2) The way they vibrate relative to the motion of the wave
Mechanical Waves In order for a mechanical wave
to exist, energy is needed to create a disturbance in an elastic medium.
Light, radio, x-rays, and gamma rays are some examples of e/m waves.
No medium is needed forELECTROMAGNETIC waves.
Electromagnetic Waves
.
ELECTROMAGNETIC WAVESAll e/m waves travel
through free space at a speed of approximately
3.00 x 108 m/s or 186,000 miles/sec.
This speed is known as the speed of light c.
The displacement of the particles of the medium is perpendicular to the direction of wave propagation.
TRANSVERSE
Parts of a transverse waveDemo slinky wave
LONGITUDINAL
The displacement of the particles of the medium is parallel to the direction of wave propagation.
Slinky demo…
Wavelengththe shortest distance
betweentwo points that are “in
phase”denoted by l and measured in units of length
Amplitudethe maximum displacement
of a particle of the medium fromthe rest or equilibrium positiondenoted by A and measured in units of length
frequency - the number of complete vibrations per unit time
denoted by f and measured in units of Hz
period - the shortest time interval duringwhich the motion of the wave repeats itself
denoted by T and measured in units of time
T = 1/f
& f = 1/T
velocity - the speed of the wavedenoted by v and measured in units of dist/time
v = d/t = l/T = f l
The speed of a wave depends on the propertiesof the medium through which it is traveling.
Example: Measurements show that the wavelength of a sound wave in a certain material is 18.0 cm. The frequency of the wave is 1900 Hz. What is the speed of the sound wave?
λ = 0.18 mf = 1900 Hz v = λ f
= 0.18 (1900) = 342 m/s
Reflectionthe turning back of a wave whenit reaches the boundary of themedium through which it is traveling
Reflection of WavesReflection from a hard boundary or fixed-end
Reflection from a soft boundary or free-end
The wave is inverted,or flipped or is a 180º out of phase
The wave is reflected right side up or remains the same, or remains in phase
Law of Reflectionthe angle of incidence is equalto the angle of reflection
Sound can also be reflected
Reflected sounds are Echoes
the bending of a wave as it passes obliquely from one medium into another of different propagation
speed
Refraction
For refraction to occur, the wave must change speed
and must enter the new medium at an oblique angle.
Refraction occurs because wave speed changes in different materials
In medium 2, the wave travels slower than in medium 1. This change in speed causes a bending toward the normal of the wave. This behavior is important in lenses
Diffractionthe spreading of a
wavearound a barrier orthrough an opening
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
Interferencethe result of the superposition of two or more waves
Interference Simulation
Superposition Principlethe displacement of the medium when two or more waves pass through it at the same time is the algebraic sum of the displacements causedby the individual wavesThese two wave pulses are moving towards each other. What will happen when they are on top of each other?
Notice that wave A has an amplitude of 2, while wave B has an amplitude of 1. Both of the wave pulses are erect, so we say that they have positive values As they come together in the middle, both of them are pulling upwards…
NOTE: They are still two separate waves, they just happen to be in the same spot at the same time.
They will continue moving on and look exactly the way they looked before they hit each other.
This is an example of Constructive Interference.
When they are directly over each other, they are both shoving particles up together, so the two waves become one big wave with an amplitude of 3 for an instant.
Notice that A and B are still the same amplitude, but now B is inverted.
For a moment the two wave pulses become one smaller wave pulse with an amplitude of (+2 + -1 = +1) positive one. This is Destructive Interference
These two wave pulses are going to collide. What will happen?
And after they pass…
Constructiveresults in a larger amplitude
Types of Interference
Destructiveresults in a smaller amplitude
adding waves