A digital spectrometer is used to measure the wavelengths of an emission spectrum of a gas. At the peak value for one of the wavelengths is found to be 489 nm. The width of the peak at half its maximum value is 1.5 nm and the width at its base is 3 nm. What is the uncertainty in the measured wavelength?

reference this link on page 146: http://www.pa.msu.edu/courses/PHY252/labfiles/Lab8.pdf