PHEN1120-Lab11
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PHEN-1120 NPU / Fall 2023 Interference and Diffraction
NAME:
Conner Woods, Olivia Whitmore, Sophia Perruffel, Michell Tejera
Lab11: Interference and Diffraction
INTRODUCTION
As long ago as the 17
th
century, there were two competing models to describe the nature of light.
Isaac Newton believed that light was composed of particles, whereas Christopher Huygens viewed
light as a series of waves. Both models could explain reflection and refraction, but the phenomena
of diffraction and interference could be more easily explained by Huygens’ wave model. In the
early 19
th
century, Thomas Young’s double-slit experiment provided evidence that supported the
wave nature of light. This is the first of two experiments that examine the related phenomena of
diffraction and interference. We will first compare the patterns that are produced when laser light
passes through one or two slits and then strikes a screen. We will then focus your attention on the
analysis of the double-slit interference pattern. We will also study the diffraction gratings.
OBJECTIVES
In this experiment, you will
Compare and contrast features of the patterns produced on a screen when light from a laser passes through either one or two slits or a diffraction grating.
Discern which features of the pattern arise from the interaction of the light with the single slit and which arise from the double slits.
Use the principle of superposition to explain how waves from two sources could interfere constructively or destructively.
Use a diagrammatic explanation of how path length differences for light passing through the
two slits give rise to bright and dark fringes in the pattern.
From experimental parameters, predict the spacing between bright (or dark) fringes in the pattern.
Analyze intensity vs.
position data to test your predictions.
MATERIALS
Diffraction Apparatus
Rules
Green Laser (532 nm wavelength)
Pasco Diffraction Place
PHEN-1120 NPU / Fall 2023 Interference and Diffraction
PASCO DIFFRACTION PLATE
B: 1 slit of 0.08 mm width
F: 2 slits of 0.008 mm width and separated by 0.25 mm
PART I / SINGLE-SLIT DIFFRACTION Q1. Report below the expected width of the central bright fringe for a laser of wavelength
λ
=
532
nm
through a single-slit of slit width a
=
0.08
mm
on a screen located a distance D
=
160
cm
from the slit.
PHEN-1120 NPU / Fall 2022 Interference and Diffraction
Q2
. Perform an error analysis between the expected value for the width of the central bright fringe
reported in Q1
and your measurement.
=2 cm for measured
=2.128 cm for expected
Percent Error: 2-2.128/2.128 x 100= -6.02%
PART II / DOUBLE-SLIT DIFFRACTION Q3. Report below the expected position of the m
=+
5
(fifth order) bright fringe for a laser of
wavelength λ
=
532
nm
through double-slit of slit separation d
=
0.25
mm
on a screen located a
distance D
=
160
cm
from the slit. Consider the zeroth-order to be located at y
=
0
.
Position of bright fringe of laser = 17.024 mm
Q4
. Perform an error analysis between the expected location of for the m
=+
5
(fifth order) bright
fringe reported in Figure 2
at 1.8 cm and your measurement.
Measured = 1.7 cm
Expected= 1.7024 cm Percent Error: 1.7- 1.7024/ 1.7024 x100%= -0.14%
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