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### Waves & Energy Transfer Chapter 14 14.1 Wave Properties Energy can be transferred by particles or by waves. Types of Waves - Mechanical, Electromagnetic, & Matter ... – PowerPoint PPT presentation

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Title: Waves

1
Waves Energy Transfer
• Chapter 14

2
14.1 Wave Properties
• Energy can be transferred by particles or by
waves.
• Types of Waves - Mechanical, Electromagnetic,
Matter
• Mechanical waves require medium to travel, such
as air, water, springs or ropes.

3
• EM waves do not require medium.
• Ex light waves, radio waves x-rays.
• They all travel at speed of light (c).
• Matter waves involve electrons other particles
that demonstrate wave like properties under
certain conditions.

4
• Will be studied under Quantum Mechanics.
• Three types of mechanical waves.
• Transverse - particles vibrate perpendicularly to
direction of motion of wave.
• Longitudinal - particles travel in direction of
wave.
• Surface - mixture of transverse longitudinal.

5
• Transverse waves do not travel through earths
center, which indicates center is fluid.
• Wave pulse - a single disturbance travels through
medium.
• Wave train or traveling wave - a series of pulses
at regular interval.

6
Two Types of Waves
7
Measuring a Wave
• Period, ? - time required for motion to repeat
itself.
• Frequency, f - number of complete vibrations per
second. f 1 / ?
• Wavelength, ? - distance from crest to crest or
trough to trough.

8
• Crests - high points of wave
• Trough - low points of wave
• When time interval is one period, wave would move
a distance of 1 wavelength.
• Velocity - given by v ? / T or v f?
• Amplitude - maximum displacement from rest or
equilibrium position.

9
• Speed of sound in air depends on temperature.
• Speed of light is always constant.
• 3.00E8 m/s c
• Ex. Prob 333
• Prac Prob 335

10
14.2 Wave Behavior -Boundaries
• When wave reaches boundary of media, it may be
reflected or pass.
• Speed ? change when wave enters new medium.
• Fig 14-7 336
• Junction of two springs is a boundary between two
media.

11
• A pulse reaching boundary (a) is partially
reflected partially transmitted. (free)
• Fig 14-8 337 A pulse is shown as it approaches a
rigid wall (a) as it is reflected from wall
(b).
• Notice amplitude is almost same but reflected
pulse is inverted.

12
• When medium changes, wave energy is both
reflected transmitted.
• Waves passing from one medium to another have
same f.
• The ? change depends on v change so that f v/ ?
is constant.
• Prac Prob 337

13
Wave Boundaries
• Less to More More to less

14
Superposition of Waves
• Principle of superposition - displacement of a
medium caused by two or more waves is algebraic
sum of displacements caused by individual waves.
• Interference - result of superposition.

15
• Destructive interference occurs when crest meets
trough.
• Resultant wave is smaller. Fig 14-11a 338
• Constructive interference occurs when waves meet
crest to crest or trough to trough.
• Resultant wave is larger. Fig 14-11b 338

16
• If waves are opposite equal magnitude, result
is 0.
• Fig 14-11c 338
• Continuous waves from a region of higher speed
to one with lower speed.
• Fig 14-12 339

17
Standing Waves
• Node - pt that is undisturbed.
• Medium is not displaced as waves pass.
• Antinode - pt of max displacement.
• Standing wave has stationary nodes antinodes.
• It is result of identical waves traveling in
opposite directions. Fig 14 -13 340

18
Waves in Two Dimensions
• Law of reflection - angle at which a wave
approaches a barrier is equal to angle at which
it is reflected.
• Fig 14-14 341
• Normal - ? to barrier.
• Angle of incidence - angle between incident ray
normal.

19
• Angle of reflection - angle between normal
reflected ray.
• Refraction - change of wave direction at boundary
between two media.
• Fig 14-15 342
• Diffraction bending of waves around barrier.
• Fig 14-16 342 Fig 14-17 343

20
Bibliography
• http//www.glenbrook.k12.il.us/gbssci/phys/mmedia/
waves/em.html
• http//www.glenbrook.k12.il.us/gbssci/phys/Class/w
aves/u10l1c.html
• http//surendranath.tripod.com/Applets/Waves/Twave
01/Twave01Applet.html
• http//www.glenbrook.k12.il.us/gbssci/phys/Class/w
aves/u10l1c.html
• Physics Principles and Problems, Glencoe
• Digital Curriculum

21
Longitudinal or Compression
22
Light Propagation
23
Wavelength
24
Fixed Boundary
25
Free End
26
Interference
27
Less to More Dense
28
Longitudinal
29
Transverse
30
Surface Waves or Water Waves
31
Destructive Constructive
32
Nodes Antinodes
33
Standing Wave
34
Diffraction