Transcript 下載/瀏覽Download

Wave Motion & EM Waves (I)
Chih-Chieh Kang
Electrooptical Eng.Dept. STUT
email:[email protected]
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： 2

1  2
1-D waves
 2 2
2
z
v t
(z, t)：wave function, v：phase velocity
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


Electromagnetic waves ： These wave do not
need a medium to propagate


Example：sound waves
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 in
opposite
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/hph.html