1. The problem statement, all variables and given/known data The fact that a laser's resonant cavity so effectively sharpens the wavelength can lead to the output of several closely spaced laser wavelengths, called longitudinal modes. Here we see how. Suppose the spontaneous emission serving as the seed for stimulated emission is of wavelength 633 nm, but somewhat fuzzy, with a line width of roughly 0.001 nm either side of the central value. The resonant cavity is exactly 60 cm long. (a). How many wavelengths fit the standing wave condition? (b) If only a single wavelength were desired would changing the length of the cavity help? Explain. 2. Relevant equations L = n λ / 2 3. The attempt at a solution n = 2L/λ n = 1895734.597 For part one I have a feeling that n is not what were solving for. (Plus I'm not using the 0.001 nm width that is given). part b. Yes it would help, because if n is an integer number, wavelengths will end up interfering constructively in the cavity.