The absorption cross-section of a single Oz molecule is approximately 7 x 10 2 my at a wavelength of 0.24 um (it increases sharply for even shorter wavelengths). Given a standard sea level pressure po of 1.01 x 10", a molar fraction for oxygen of 21%, a mean molecular mass m for air of 29 kg kmole , a gravitational acceleration of 9.81 m s-2, and Avogadro's constant NA = 6.02 x 10" kmole , compute: 1. The mass per unit area of the atmospheric column assuming hydrostatic balance. 2. The number of oxygen molecules per unit area in the column. 3. The optical thickness and vertical transmittance due to molecular oxygen at 0.24 um