4. The full width at half maximum of an atomic absorption line at 589 nm is 100 MHz. A beam

of light passes through a gas with an atomic density of 10¹7/m³. Calculate:

(a) the peak absorption coefficient due to this absorption line. You can assume that the

index of refraction is close to 1 in for this dilute gas;

(b) the frequency at which the resonant contribution to the refractive index is at a

maximum;

(c) the peak value of this resonant contribution to the index of refraction.