Calculate the ratio of the rates of stimulated emission to spontaneous emission for a HeNe laser operating at 632.8nm. The laser has an output power of 1mW and a beam diameter of 1mm. The output mirror has 1% transmission at the laser wavelength and the width of the fluorescent line-shape is delta-nu =1.5GHz. Compare the rates at the central operating frequency. Hint: calculate A/B21 then invert it. Multiply by g(nu) I/c to get the required ratio. n.b. the ‘I' in the formula is Irradiance, check the definition.