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Wave Motion & EM Waves (I)
Chih-Chieh KangElectrooptical Eng.Dept. STUT
email:kangc@mail.stut.edu.tw
What is light?
Light is an electromagnetic wave consisting of an oscillating electric and magnetic field.
Light exhibits wave phenomena, such as interference and diffraction etc..
…
What are waves?
What Are Waves? Physically, a wave is a vibrational disturbance
from a normal or equilibrium condition that propagates through a medium or space.
Example : sound waves, light waves, radio waves, microwaves, water waves, sine waves, cosine waves, Mexican waves, traffic waves, earthquake waves, waves on a string, and slinky waves.
Mathematically, Waves are solutions to the wave equation :
1-D waves
(z, t) : wave function, v : phase velocity
2
2
22
2 1
tvz
Physical Interpretation of Waves Wave propagation describes
the spreading of a disturbance
Waves transfer energy, momentum from one point to another without the transport of matter
Medium : a substance which carries a wave (disturbance) from one location to another
Example : water, air, solid materials
Type of Waves Mechanical waves : These need a
medium to propagate in Example : sound waves
Electromagnetic waves : These wave do not need a medium to propagate Example : light waves
Matter wave : Particles such as protons and electrons can be treated as waves
Classification of Waves By orientation - longitudinal wave or
transverse wave By appearance - traveling wave or
standing wave By dimension - Dimensionality (1D, 2D,
3D) By duration - periodic wave or pulse
wave
Classification of Waves Longitudinal wave : distrbance is parallel to
the direction of travel - slinky waves
transverse wave:Disturbance is perpendicular to the direction of travel - waves on a string
Longitudinal waves & Transverse Waves
(Hecht)
Classification of Waves Traveling waves : A wave that
propagates in a transmission medium Standing waves : A stationary pattern
of wave is formed by the superposition of two waves of the same frequency propagating inopposite directions(Serway)
Classification of waves One-dimensional
waves (1-D)
Two-dimensional waves (2-D)
Three-dimensional waves (3-D)
Classification of Waves Pulse waves : Disturbance is
momentary and suddenly
Periodic waves : Disturbance repeats at regular intervals
(Serway)
Characteristic of Waves
crest : the highest point of the wave that is elevated above the equilibrium condition
trough : the lowest point of the wave that is depressed below the equilibrium condition
References E. Hecht, Optics, Addison-Wesley. R. A. Serway, Physics for Scientists and
Engineers with Modern Physics, Saunders. J. D. Cutnell, and K. W. Johnson, Physics, Wiley. http://hyperphysics.phy-astr.gsu.edu/hbase/hp
h.html
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