If you take the model in Ex. 4.1 at face value, what natural frequency do you get? Put in the actual numbers. Where, in the electromagnetic spectrum, does this lie, assuming the radius of the atom is 0.5 A? Find the coefficients of refraction and dispersion and compare them with those for hydrogen at C and atmospheric pressure: A = 1.36 x 10–4, B = 7.7 x 10–15m2.