Introduction

The Single-Slit diffraction experiment is amazing !

“The Action Lab” has conducted the experiment using an crescent wrench with 2 razor blades and a laser pointer:

This 3D model provides a magnetic holder for two razor blades to form an adjustable single slit and a holder for a laser pointer.

Let's repeat the experiment !

Materials

• 1 x laser pointer (e.g. LASERFUCHS Punktlaser Lasermodul rot 650nm 1mW)
• 2 x razor blades (e.g. Wilkinson Sword Classic Vintage Edition / Wilkonson Classic Shave Double Edge Blades )
• 4 x magnets (5 mm diameter, 1 mm height)
• 1 x screw 3x20 mm, hex head
• 1 x nut M3
• glue

3D Printing the Model

Step 1

• Decide if you want to use the gcode file or if you want to slice the STL file.

If you want to slice the STL file it is recommended to

• print in PLA
• use 3 perimeters
• use 20% infill
• use 0.2 mm resolution
• add a pause to insert the 4 magnets

Step 2

• Ensure 4 magnets are available
• Start the 3D print
• Wait until the printer pauses
• Put the 4 magnets into the slots
  
   
• Resume the 3D print
• Final result
   

Assemble 

Knob

• Add some glue to the knob
• Insert the screw to the knob

Single-Slit

• ensure the right blade holder can freely moved, you may need to use a bit of force to the left and to the right

• Insert the M3 nut
• Insert the screw with knob

Razor Blades

• Caution: Don't touch the sharp edges of the razor blades ! 
• Add the razor blades by holding them on the non-sharp edges (the magnets will hold the razor blades)

• Turn the screw so that just a small slit between the blades is visible

Laserholder

• Assemble the laser holder and single-slit with razor blades
• Place the laser pointer on the laser holder

Safety

Read and follow the safety instructions of your laser pointer.

NEVER put yourself into any position where your eyes approach the axis of the laser beam (even with eye protection on). Keep beam paths below or above standing or siting eye level. Do not direct them towards other people or animals.

Conduct the experiment

• Place the holder so that the laser beam points to a wall with a distance of 2 .. 5 m
• Switch on the laser pointer
• By adjusting the slit width the pattern changes:

Change the 3D model to your needs

An OpenSCAD file has been attached - don't hesitate to change the model to your needs.

The 3D model is simple and there are many areas for future improvement:

• the freely moveable razor blade holder should stick to a position. 
• the screw should snap into the knob so there is no need for glue
• by one revolution of the M3 screw the slit width changes by 0,5 mm. This may be improved to a smaller value e.g. by using gears.
• Currently just one razor blade is moved when turning the screw - it would be nice if both blades are moved.

Disclaimer

Conduct the experiment on your own risk.  I will not be responsible for any accidents, injuries or illness.