Experiment 11: CD Diffraction

Purpose:

The purpose of this experiment is to measure the wavelength of a laser and to measure the distance between the grooves on CD using diffraction.

Experiment:

The wavelength of the laser can be measure using a diffraction grating.

Diffraction pattern can be seen on the board when laser passes through
a diffraction grating

The wavelength can then be calculated as follow

where: L = distance from diffraction grating to the white board
           d = width of slit on the grating
           y = distance between 2 maxima

To measure the distance between the grooves on CD, the following setup is used

Laser is reflected off of the CD and diffraction pattern is
observed on a piece of paper.

The distance between grooves can then be calculated as follow

This value gives us an error of 87% when compared with the expected value which is 1600nm

Conclusion:
Although the experiment has a really high error, we can still see that with more careful measurement, the distance between the grooves on CD can be calculated by applying the concept of diffraction. The reason of the large error in this experiment is mostly because the paper and the CD may not be exactly parallel.