Laboratory 6

Diffraction patterns

Objective:

In this lab students will study the diffraction patterns of slits and circular apertures.  They will study the patterns in the Fraunhofer regime.

Equipment:

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Laser Assembly

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Beam Steering Assemblies

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Lens Chuck Assemblies

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Target Assemblies

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Lens Kit

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Targets

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Meter Stick

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Index Cards

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Project in Optics Workbook

Procedure:

Students will use the instructions on pages 59 - 66 of the Projects in Optics Workbook as a guide.  To assemble the components, students will refer to pages 36 - 44 in the Projects in Optics Workbook. 

Part 1:

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Fraunhofer diffraction of a circular mask

Construct a table as shown below.

  TP2 TP3

pinhole-target distance (L)

   
diameter of first dark band (a)     
measured sinθ ~ θ ~ a/(2L)    
diameter of pinhole (D)    
predicted θ = 1.22λ/D    
D2/Lλ    

Evaluate if your measurements were made in the Fraunhofer regime.  Your measurements were made in the Fraunhofer regime if D2 << Lλ.
Link: When is the Fraunhofer approximation valid?
 

Part 2:

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Single slit diffraction and double slit interference

Construct a table as shown below.

  Single Slit

slit-target distance (L)

 
distance between dark bands (a)   
measured sinθ ~ θ ~ a/L  
slit width (w)  

 

slit-target distance (L)

Double Slit
distance between maxima (a)   
measured sinθ ~ θ ~ a/L  
slit separation (d)  

 

slit-target distance (L)

Grating
distance between central and first-order maximum (a)   
measured tanθ = a/L  
groove separation (d)  
number of grooves/mm  

 

Laboratory Report:

Open Microsoft Word and prepare a report using the template shown below.

Name:
E-mail address:

Laboratory 6 Report

bulletIn a few words, describe the experiment. (What?)
bulletIn a few words, state the objective of the experiment. (Why?)
bulletComment on the procedure.  Did you encounter difficulties or surprises? (How?)
bulletPresent your results and comment on your results.