PASCO OS-8529 SLIT ACCESSORY - Manual (Page 11)

012–06348A Slit Accessory
7
Figure 3.2: Interference Fringes
Theory
When diffraction of light occurs as it passes through
a slit, the angle to the minima in the diffraction pattern
is given by
where a is the slit width, θ is the angle from the center
of the pattern to the m th minimum, λ is the wavelength
of the light, and m is the order (1 for the first
minimum, 2 for the second minimum, . . . counting
from the center out). See Figure 3.1.
When light passes through two slits, the two light
rays emerging from the slits interfere with each other
and produce interference fringes. The angle to the
maxima (bright fringes) in the interference pattern is
given by
where d is the slit separation, θ is the angle from the
center of the pattern to the m th maximum, λ is the
wavelength of the light, and m is the order (0 for the
central maximum, 1 for the first side maximum, 2 for
the second side maximum, . . . counting from the
center out). See Figure 3.2.
Experiment 3: Comparisons of Diffraction and Interference Patterns
The purpose of this experiment is to compare the diffraction and interference patterns formed
by laser light passing through various combinations of slits.
a sin θ = m λ (m = 1, 2, 3 . . .)
d sin θ = m λ (m = 0, 1, 2, 3 . . .)
a
m = 2
m = 1
m = 2
m = 1
slit
θ
screen
Figure 3.1: Single Slit Diffraction Pattern
screen
slit
θ
diffraction envelope
m = 0
m = 5
m = 1
m = 2
m = 3
m = 4
d
Materials required:
• optics bench 1 • white projection surface
• Diode Laser (OS-8528) • metric rule
• Single Slit and Multiple Slit Sets (OS-8529) • page 2 of the Slit Accessory manual
1 From the Introductory or Advanced Optics System (OS-8500 or OS-9254A)
Purpose