Question

In a stellar atmosphere, the radiation intensity passing through various layers is given as I_out = (I_in)e^(−τ) .

1. a) How large must the optical depth through a material be for the material to absorb 50% of the incident photons, as in the solar photosphere?

2. b) Regions in the solar chromosphere have an optical depth of τ = 0.1. What fraction of the Sun’s radiation intensity is transmitted through this region?

3. c) In the optically thin limit, I_out = I_in*e^−τ reduces to I_out = I_in*(1 − τ ). Based on this definition, are either the photosphere or chromosphere considered to be optically thin?

Answer 1