Can a Red Laser Create Beautiful Diffraction Patterns with Limited Materials?

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    Diffraction Patterns
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Discussion Overview

The discussion revolves around methods for creating diffraction patterns using a red laser, particularly in a setting with limited materials. Participants share various techniques and suggestions for generating interesting visual effects through diffraction, exploring both practical applications and experimental setups.

Discussion Character

  • Exploratory
  • Technical explanation
  • Homework-related
  • Experimental/applied

Main Points Raised

  • One participant inquires about suggestions for creating diffraction patterns with a red laser in a resource-limited environment.
  • Another suggests using an old CD or DVD as a diffraction grating and mentions constructing single and double slits with razor blades and thin wire.
  • Participants recommend experimenting with various objects, such as frosted light bulbs and coins, to observe diffraction effects in different settings.
  • One idea involves using a beam expander to create a larger laser beam and observing the diffraction pattern created by a suspended coin.
  • Another participant proposes using a hair to measure thickness based on the diffraction pattern produced when the laser shines on it.
  • Suggestions include creating a tiny pinhole in foil to observe circular aperture diffraction patterns.
  • A participant mentions the potential use of a laser printer and transparency sheets to create gratings for diffraction experiments.
  • One participant advises against focusing on equations initially, suggesting that observation should guide the understanding of diffraction patterns.
  • Another introduces the concept of using oblique reflections and oscillating gates to manipulate the laser beam and its diffraction effects.
  • A calibration method is proposed to measure hair thickness by comparing it to known wire thicknesses and analyzing the resulting diffraction patterns.

Areas of Agreement / Disagreement

Participants generally agree on the various methods to create diffraction patterns, but there are multiple competing views on the best approaches and the importance of theoretical equations versus practical experimentation. The discussion remains open-ended without a consensus on a single method or approach.

Contextual Notes

Some suggestions depend on the availability of specific materials, such as laser printers or certain types of wire, which may not be accessible to all participants. Additionally, the effectiveness of various techniques may vary based on environmental conditions and setup specifics.

p.tryon
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Hi
I was wondering whether anyone could suggest ways of making nice diffraction patterns using a red laser. I work at a charitable school in Kazakhstan so am limited in terms of materials. Any suggestions would be appreciated. Thanks
 
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What kind of diffraction patterns do you want to look at?

Do you have an old CD or DVD laying around? Bouncing a laser off of that, it acts as a diffraction grating.

You can use two razor blades mounted to make a nice single slit. You can even put a thin wire between them on one end, and make the blade edges touch at the other, and have a continuous variable width single slit.

I've seen double slits made with two razor blades and a thin wire.
 
Turn the lights off in the lounge or kitchen etc .. and fire the laser beam at all sorts of stuff ..

Personally i like aiming at frosted or florescent light bulbs , but you will find all sorts of objects that work well in this regard (especially glancing angles where you aim at the edge of an object .
 
Two more ideas. One that was done at my university and the photos featured in the Serway undergrad text...if you have a beam expander, make the beam larger than whatever small coin you have there. We generally use a penny or a dime, which are 9.25mm and 8mm in diameter, and are suspended by the thinnest thread we can find. When projected in a dark room, with a good expanded beam, you can see the shadow of the coin within the beam on a target some distance away. You will also see a bright spot in the CENTER of the target--a bright spot that can only be there because of diffraction. If it isn't clear, try moving the target closer or farther away--I don't recall the exact distance we used, but it was within an indoor laboratory.

Also, try stretching a hair straight and shining the laser on it. Try different hairs--see if the students can rank the hairs by thickness based on the diffraction pattern.

Use a piece of foil--even a candy wrapper--and make a tiny pinhole in it. I have made really small ones by placing the foil on a piece of glass, and tapping the pin on the surface of the foil. You'll see a circular aperture diffraction pattern--bright center spot, alternating dark/light rings.
 
I found another I remembered--do you have a decent laser printer and transparency sheets that will work in it?

http://physics.bgsu.edu/~vanhook/gratings/
 
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I love this site! Thank you so much for all these great ideas. I will try experimenting. The laser jet prints look amazing but I don't think we have the laser jet :-(

P.S. if we were investigating hair width based on the diffraction pattern is there an equation we would need?

Thanks again!
 
I would investigate first without an equation if i was you p.t .
Bring forth equation from observation is a encouraging cycle .

Another thing to mention is that by reflecting the coherent bean obliquely off an object you can achieve a primary dispersion pattern ..

The secondary linear filtering of this pattern through a window can reduce the Photon beam considerably .. which can be interesting .

Also using some small electric fans as oscillating gates the beam can be further reduced in volume ..

cheers
 
You could "calibrate" the hair-measuring laser setup by using wire of known thickness...maybe magnet wire. Measure the characteristics of the diffraction pattern with the various thicknesses of wire, look for a mathematical relationship between the pattern and the wire thickness, then interpolate or extrapolate to the thickness of the hair.
 

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