Ch. 36:
Diffraction - Part A
1
December 7, 2009
Chapter 36:
Diffraction
!
Young’s interference experiment.
!
Examples of interference.
!
Two HITT questions.
!
Single-slit diffraction.

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Ch. 36:
Diffraction - Part A
2
December 7, 2009
Young’s Interference Experiment
!
Thomas Young (1773-1829), an English polymath,
proved in 1801 that light is a wave.

Ch. 36:
Diffraction - Part A
3
December 7, 2009
Young’s Interference Experiment
!
The interference pattern is determined
by the path length difference
∆
L
of the
rays reaching a point P on the screen.
!
d
is the distance between the two slits.
!
Angle
θ
specifies the location of the
bright and dark fringes on the screen.
!
Need to relate
θ
,
∆
L
,
d
and
λ
.
!
∆
L
is the distance
S
1
to
b
.
!
Assume that the screen distance
D
is
much greater than
d
, thus
r
1
and
r
2
are parallel.
sin
θ
∆
=
L
d
sin
θ
λ
λ
∆
⇒
=
L
d

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