Diffraction

Diffraction

When light (or any wave) encounters a barrier but passes through small holes that are about the same size of the wave, diffraction occurs. The waves are bent in a characteristic pattern. The holes are called diffraction slits. Diffraction can be used to separate white light into its separate colors
(wavelengths). Diffractions slits are common in scientific
instrumentation for this purpose.

 

 

Video Demonstrations

1) Animation of Double Slit Diffraction

2) Film of an actual Double Slit Experiment

 

Materials – Difraction
CD diffraction gratings

• 6 CD’s with silver backing removed
• laser pointers
  
  

Atomic Emission Spectra

• diffraction gratings or spectroscopes
  
• element tubes for emission spectra (Mercury, Deuterium)
• incandescent light bulb
• light bulb adapter
• powerstrip
  
  
  

Simple Model of Diffraction

1. Shine the laser pointer at the single CD.  There will be a simple diffraction pattern on the wall.

 

2. Shine the laser pointer at 2 overlapped CD’s.  The new diffraction will be more complex.  How?

   

3. Now shine the laser pointer at 3 overlapped CD’s.  What do you expect to see?

Emission Line Spectra

1. Look at the incandescent light through the diffraction grating.  There should be a continuous pattern of the colors of the rainbow.  The diffraction grating can separate the colors of the emitted light into its separate components.
   
   
2. Now look at the other lamps.  The emission spectrum will be discontinuous and contain only some colors of the rainbow.
   
   

 

 

Notes
 Coming soon.