a). The half of the sphere facing the beam has surface area of
2 (pi) (R²)
= (2 pi) (633 x 10⁻⁹ m)²
= (2 pi) (4.01 x 10⁻¹³) m²
= 2.52 x 10⁻¹² m²
Average power = (5 x 10⁻³ W) / (2.52 x 10⁻¹² m²)
= 1.984 GW / m² .
b).
c).
d). I don't remember how to do these parts of the question.
However, I do sincerely believe that the solution of part-'a' was
a fair return for the penurious and parsimonious award of 5-points.
