Question

a. what is your average computed value of the track spacing for CD? Calculate the percent difference between your measured value and the value specified in the compact disc standard: 3.2 um.

b. does you average value of the CD track spacing fall within the tolerance of +- 0.1 um given in the compact disc specification?

Answer 1

Solution of a:

Here,
Distance between slits, track spacing
Distance from screen to slits (here, compact disc)
Wavelength of the light

Since, we do not have angle value for fringe order , we cannot use , therefore, we are using the practical distance from central maxima to first   bright fringe.

Using the scale given in image, we found practical distance from central maxima to first   bright fringe is:

We have formula for diffraction grating:

Therefore, the measured track spacing in CD is 3.4 micrometre.

Percent difference between standard compact disc track spacing and measured track spacing is given by:

Solution of b:

The tolerance for track spacing does not fall within   but it falls within . Using angle value and equation may give us tolerance within  .