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:

	Laser Assembly
	Beam Steering Assemblies
	Lens Chuck Assemblies
	Target Assemblies
	Lens Kit
	Targets
	Meter Stick
	Index Cards
	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:

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:

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

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