PHYS 214 PSU Single Slit and Double Slit Interference Lab ONLY do the questions makred in the green box. The instructions are clear and the whole document

PHYS 214 PSU Single Slit and Double Slit Interference Lab ONLY do the questions makred in the green box. The instructions are clear and the whole document is in the attachment. PHYS 214
Laboratory
Diffraction
Light Interference & Diffraction with
Single and Double-Slits
Areas where you are asked to input something are marked with green boxes .
Score: _____
Name:_____________________________
Section #:______
Name:_____________________________
Section #:______
Name: _____________________________
Section #:______
Lab-Specific Goals
•
•
•
•
Measure the pattern formed by the interference of light passing a single slit
Measure the interference pattern from two slits
Experimentally verify the single and double slit diffraction equations
Experimentally calculate the slit widths
Course objectives measured in this lab
1.4. Solving problems involving interference in two dimensions such as the double slit
experiment.
1.5. Describing quantitatively the pattern produced by single-slit diffraction.
Reading in the textbook
Knight, 4th edition. Chapters 33.2, 33.4
Equipment
•
•
•
•
•
•
•
•
Diode laser (OS-8525) with power supply
Optics bench with centimeter scale
Single Slit Disk (OS-8523)
Multiple Slit Disk (OS-8523)
Aperture Bracket (CI-6538) for Light sensor with Post
Light Sensor with cable
Rotary Motion Sensor (CI-6538)
Linear Motion Translator
• PASCO 550 Universal Interface
1
PHYS 214
Laboratory
Diffraction
The light sensor reads out a voltage in Capstone which is proportional to the intensity of
the light that is incident upon the sensor aperture.
Introduction
Open your textbook (either hardcopy or use the ebook in Mastering Physics). Studying
single and double slit diffraction illuminates the wave nature of light.
Diffraction with a single slit
The intensity as a function of angle  for a single slit is not in the book. It can be derived
by adding an infinite sum of waves (an integral) for each point in the single slit (using
Huygens’ principle). The result is
= 0 [
sin
)

sin

sin(
2
] = 0 (
sin 2

)
Eqn. 1
where
=
sin
Eqn. 2

a is the slit width and  is the wavelength of the light used. Io is the intensity at  = 0,
corresponding to the principal maximum.
Interference & diffraction with a double slit
Consider a double slit setup consisting of two long parallel slits each of width a and
separated by a distance d. The transmitted intensity is given by
= 4 0 [
sin
)

sin

sin(
2
sin
] [cos (

2
sin 2
)] = 4 0 (

) cos2
Eqn. 3
where  was defined in eqn. 2 and
=
sin

Eqn. 4
2
PHYS 214
Laboratory
Diffraction
Introductory questions
1. Draw a single slit setup (on the left side of the box below) and the corresponding
light intensity function along a screen (on the right side of the box below)
showing the diffraction. If there is only one slit what causes the interference?
Explain using Huygens’ principle.
2. What are the conditions for  in Eq. 1 such that there is a diffraction minimum?
Use this condition in Eq. 2 to derive Eq. 33.19 in your textbook. Why does  = 0
not work as a solution?
3
PHYS 214
Laboratory
Diffraction
3. Draw a double slit setup and the corresponding interference pattern (the
Intensity versus position on the screen). Explain why there is a factor of 4 in Eq.
3 by considering: (i) what happens to the amplitude of the electric field of the
light wave when there is light through two slits instead of one, and (ii) how is the
light intensity related to the electric field amplitude?
4. If  in Eq. 4 controls the double slit interference pattern in Eq. 3, what are the
conditions on  such that there is an interference minimum? Use this to derive
Eq. 33.8 in your textbook.
4
PHYS 214
Laboratory
Diffraction
Setup
The experimental set-up for this activity is shown in Figures 1 and 2. The laser light is
passing through a slit and falling on the aperture bracket, which selects the light at a
fixed position only. The light sensor is then measuring the intensity of the light at that
point.
Exploration
1: A Single Slit
1. Set up the laser, single slit disk, and the light sensor on the optical bench as
seen in Figure 2. Record the wavelength of your laser in nm.
Do not look into the laser or point it toward someone’s eyes.
2. The single slit disk should be close to the laser and far from the light sensor.
Why does the disk need to be far from the light sensor? Study the
assumptions made in Figure 33.5 in your book as a guide to answer this
question.
5
PHYS 214
Laboratory
Diffraction
You should be able to see the diffraction pattern on the aperture bracket
surface.
3. Choose the slit width a = 0.04 mm, and set the aperture bracket to position #3;
make sure that the diffraction pattern is horizontal. The laser beam should be
centered on the single slit.
4. Connect the light sensor and the rotary motion sensor to PASCO 550 Universal
Interface. Do this by selecting the connection with the yellow cable in PASCO.
Under “Properties” of the rotary motion sensor, change the resolution to high,
and the “Linear Accessory” to “rack and pinion”.
5. The light sensor can be over-saturated, this effect is visible as artificial plateaus
in your data within PASCO. To avoid over-saturation you should experiment
with the gain setting of the light sensor (toggle switch on top), and the
sensitivity of the light sensor in PASCO Capstone.
6. Make sure that:
• The Rotary Motion Sensor’s sample rate should be set at 50Hz for best
performance.
7. What must you measure, using the light sensor, to verify the diffraction shape
predicted by Eq. 1? What quantity in PASCO can you use to measure this?
6
PHYS 214
Laboratory
Diffraction
8. Make sure that you move the light sensor on its track so that you measure the
entire diffraction pattern. How does the speed with which you move the light
sensor affect your data quality? Does going slow or fast produce better data?
9. Make the appropriate graph to display the intended physics. Attached your
graph to this lab report (and write Q9 on it). There will be multiple graphs in
this lab. You can join them all in one single word document (use a snapshot tool
to get the images) and print at the end.
10. Repeat the experiment with some other slit width a. Record the new width and
attached the new graph to this lab report (write Q 10 on it).
11. Looking at your graph(s), where are the m=1 minima? m=2 minima? Fill in the
table below for each slit width: the first row for the 0.04 mm slit and use the
second row for your measurements of the second slit. Determine the slit
width twice using the m =1 minima and then the m=2 minima and determine
the % difference between each calculated width and the given value for the slit
wit (recall difference when 2 numbers are both calculated is |value1value2|/(average value)x100 ).
Distances
Slit
a
(mm)
Slits to
Screen
Center
to m=1
Center
to m=2
Calculated
Slit Width 1
Calculated
%
Slit Width 2 Difference
#1
#2
7
PHYS 214

Laboratory
Diffraction
12. Does the distance between minima increases or decreases when the slit width
is increased (or decreased)? Do your experiments support this?
8

Purchase answer to see full
attachment