b) A Fabry-Perot device contains two parallel part-reflective surfaces, each with a power re- flection coefficient R = 0.92, separated by an air gap of 40 μm. The device is used at a small but non-zero angle of incidence, such that there is a transmission maximum at wavelength 589 nm. Calculate the coefficient of finesse, and the resolving power. If a sodium lamp emits 2 spectral lines at 589.0 and 589.6 nm respectively, comment on whether these two lines can be resolved by the device.

b) A Fabry-Perot device contains two parallel part-reflective surfaces, each with a power re- flection coefficient R = 0.92, separated by an air gap of 40 μm. The device is used at a small but non-zero angle of incidence, such that there is a transmission maximum at wavelength 589 nm. Calculate the coefficient of finesse, and the resolving power. If a sodium lamp emits 2 spectral lines at 589.0 and 589.6 nm respectively, comment on whether these two lines can be resolved by the device.