Human body radiation and solar radiation Goals: Understand “energy budget sheet” of human body; Understand solar radiation and solar radiation constant.

Q01 Which of the following is true? A)The total radiation power of a blackbody doesn’t depend on the surface area. B)Two black bodies with identical temperatures and surface areas can radiate with different power if shapes are different. C)The colder the black body, the more radiation it emits. D) The radiation power per unit area only depends on temperatures.

Q02 Which of the following is true? A)The dominating radiation from a human body is in the microwave range; B)This class room mainly radiates radio waves; C)The radiation power per unit area from a human body is higher than from boiling water; D) The sun not only radiates visible lights but also infrared waves and ultraviolet lights.

Human body energy budget sheet Human body as a black body at temperature 37C radiates with power ~900W (for A=2m^2). Energy intake from food is about 2,000 Cal per day. Is the energy balanced?

Q03 An astronaut without a space suit steps outside a space station and quickly loses heat because A) the astronaut radiates more energy than he takes from food; B) the astronaut radiates more energy than he takes from the space around it; C)the empty space doesn’t radiate enough energy back to the human body to balance the energy flow; D) the human body radiates less energy than the sum of energies it takes from the empty space and food.

Solar radiation constant Solar radiation intensity near the earth is called solar radiation constant. It is about S=1367W/m^2. Why not higher or lower?

Power per unit area versus the distance