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Using Diffraction Patterns to Measure Data Track Spacing

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cece tran

on 13 March 2014

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Transcript of Using Diffraction Patterns to Measure Data Track Spacing

Using Diffraction Patterns to Measure Data Track Spacing
The purpose of this project is to measure the pitch (spacing) of the data track on CDs and DVDs. After recieving all the information then comparasions are made between the values of the angles.
The bigger the angles made from the diffraction of the laser, the more space availiable on the disc.
1. Place the CD, label down, near the center of the workspace.
2. Put a piece of cardboard to the right of the CD and another one behind the CD.

Procedure (cont.)
3. For measuring the angles, attach the protractor to the index card, flush at the bottom. Then use a stack of 2 cardboard spacer so the laser can shine down between the index card and protractor.
4. Tape the index card and protractor to the side of the box
Procedure (cont.)
5. Carefully place the box over the CD and cardboard pieces. The index card shoulld be lined up along the diameter of the CD and parallel to the front of the table. The center of the protractor should be lined up midway between the center and rim of the CD.
Procedure (cont.)
6. Direct the laser pointer beam down the face of the index card, and align the beam with the center of the protractor. Adjustment carefully, keeping the beam as close to parallel with the card as possible.
7. When the incident and diffracted beams are clearly visible, mark their locations with a marker.
Procedure (cont.)
8. Repeat the procedure at least three times.
9. Do three trials with a DVD for comparison.
10. Fill out chart
Procedure (cont.)
11. Calculate using this formula
d = m × λ / (sin θm − sin θi )
Data (cont.)
- Laser pointer with known wavelength
- CD and DVD
- Protractor
- index card
- several pieces of thin cardboard
- sturdy box
- marker
- calculator
The larger angles has more availiable space in the disc which means you can add more music to it.
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