9/17/2010
It is against the honor code to “click” for
someone else-violators will loose all clicker pts.
HITT RF Remote Login Procedure:
It is against the honor code to “click” for
someone else-violators will loose all clicker pts.
HITT RF Remote Login Procedure:
The radio channel number for this room is “09” (zero, nine).
It is STRONGLY recommended to login your remote for every class just
to be sure it is on the correct radio channel and working before class.
1.
2.
3.
4.
The radio channel number for this room is “09” (zero, nine).
It is STRONGLY recommended to login your remote for every class just
to be sure it is on the correct radio channel and working before class.
PRESS AND HOLD THE DOWN ARROW KEY until
the GREEN light on the remote turns RED.
PRESS THE “0” KEY and you will see the RED light
flash GREEN.
PRESS THE “9” KEY and you will see the RED light
flash GREEN.
PRESS AND RELEASE THE DOWN ARROW KEY
again and you will see the red light search for the
receiver, if it BLINKS GREEN MULTIPLE TIMES you
are logged in.
PRESS AND HOLD THE DOWN ARROW KEY until
the GREEN light on the remote turns RED.
PRESS THE “0” KEY and you will see the RED light
flash GREEN.
PRESS THE “9” KEY and you will see the RED light
flash GREEN.
PRESS AND RELEASE THE DOWN ARROW KEY
again and you will see the red light search for the
receiver, if it BLINKS GREEN MULTIPLE TIMES you
are logged in.
1.
2.
3.
4.
For Interference to Occur
Wave Optics
The wave nature of light is needed to explain various
phenomena
 Interference
 Diffraction
 Polarization
The particle nature of light was the basis for ray
(geometric) optics


Interference


Light waves interfere with each other much like
mechanical waves do
All interference associated with light waves arises
when the electromagnetic fields that constitute the
individual waves combine








Thomas Young first
demonstrated interference
in light waves from two
sources in 1801
Light is incident on a
screen with a narrow slit,
So
The light waves emerging
from this slit arrive at a
second screen that
contains two narrow,
parallel slits, S1 and S2
They must maintain a constant phase with respect
to each other-wave go up and down together in
time
The waves must have identical wavelengths
Thomas Young first demonstrated interference
in light waves from two sources in 1801
Light is incident on a screen with a narrow slit,
So
The light waves emerging from this slit arrive
at a second screen that contains two narrow,
parallel slits, S1 and S2
Fringe Pattern
Young’s Double Slit Experiment

The sources must be coherent



The fringe pattern formed
from a Young’s Double
Slit Experiment would
look like this
The bright areas
represent constructive
interference
The dark areas represent
destructive interference
http://h2physics.org/?cat=48
1
9/17/2010
Bright bands
Interference Patterns

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Constructive interference
occurs at the center point
The two waves travel the
same distance
 Therefore, they arrive
in phase-a bright fringe



The upper wave travels onehalf of a wavelength farther
than the lower wave
The trough of the bottom
wave overlaps the crest of the
upper wave
This is destructive interference
 A dark fringe occurs


The path
difference,
Understanding
δ, is found from the
beige triangle
δ = r2 – r1 = d sin θ


the Fringe Pattern
This assumes the
paths are parallel
Not exactly parallel,
but a very good
approximation since
L is much greater
than d




Ө
Definition of sin θ = δ/d
Or
d sin θ = δ
Definition of tan θ = y/L
For small θ: tan θ = sin θ



The positions of the fringes can be measured
vertically from the zeroth order maximum
y = L tan θ  L sin θ
Assumptions: L>>d and d>>λ
Approximation
 θ is small so tan θ  sin θ
For bright fringes
y bright 
For dark fringes
ydark 
Bright fringe, produced by constructive interference,
path difference must be either zero or some integral
multiple of the wavelength λ
δ = d sin θbright = m λ
 m = 0, ±1, ±2, …
When destructive interference occurs, a dark fringe is
observed
This needs a path difference of an odd half wavelength
δ = d sin θdark = (m + ½) λ
 m = 0, ±1, ±2, …
δ
Position of Fringes on the y-axis

Light and Dark Fringes

Three right Triangles!

The upper wave has to travel farther than the lower
wave
The upper wave travels one wavelength farther
 Therefore, the waves arrive in phase
Bright fringes occur when the path length differs by
exactly mλ
L
L 
d
m
1
m 
d 
2
m  0,  1,  2 
Quick Quiz
What is the difference in light path lengths
which produce the dark bands in the Young
2-Slit Interference Pattern?
A.
B.
C.
D.
E.
mλ
(m+1) λ
(m+½) λ
(m+¾) λ
Can not be predicted
m  0,  1,  2 
2