Light can deliver energy to a surface that it illuminates, as you can appreciate if you have ever warmed yourself in the Sun on a cold day. The equation for the power of sunlight on a surface is P = IA cos θ, where P is the power, I is the "intensity" of the sunlight (roughly, its brightness), A is the area of the surface, and θ is the angle between the light and the area vector. This is a "light" analogy of the electric flux through a surface, with power playing the role of flux. (a) The circular disk of a sunflower head has a radius of 13.5 cm. The intensity of direct sunlight at the Earth's surface is 1240 W/m^2. What is the light power P received by the sunflower disk when it points directly at the Sun, that is, when its area vector is parallel to the direction of the sunlight? (b) The photograph of sunflowers that accompanies this problem was taken at 5:00 P.M., when the angle of the Sun from the zenith was 73.3°. If sunflower blossoms always pointed straight up (as daisies do), what power would the sunflower disk described in part "a" be receiving at 5:00 P.M.?