A person with skin area 2 m2 and 0.97 radiation efficiency is at rest and has a skin temperature of 28o C in an environment with a uniform temperature of 22o C. Calculate the heat loss rate if the skin temperature is raised by 8o C by vigorous exercise.

The next four questions use this description.  Our Sun has a peak emission wavelength of about 500 nm and a radius of about 700,000 km. Your dark-adapted eye has a pupil diameter of about 7 mm and can detect light intensity down to about 1.5 x 10-11 W/m2.  Assume the emissivity of the Sun is equal to 1. First, given these numbers, what is the surface temperature of the Sun in Kelvin to 3 significant digits? What is the power output of the Sun in moles of watts?  (in other words, take the number of watts and divide it by Avogadro's number) Assuming that all of the Sun's power is given off as 500 nm photons*, how many photons are given off by the Sun every second? Report your answer to the nearest power of 10 (e.g. if you got 7 x 1024, give your answer as 25).

A) Estimate the total solar heating absorbed by the Earth every second. Assume 36% of the incoming solar radiation is reflected by clouds and lost. You can assume that the Earth intercepts sunlight with an effective area of πr2 where r is Earth’s radius. B) Estimate the total heat lost by the Earth as infrared radiation every second. Assume Earth has an  effective temperature of 252 K (-21 C).

Calculate the amount of radiation emitted for a unit surface (1 m²) for the following situations. Express your answers in both SI units (in W) and U.S. Customary units (in Btu/h). (a) a hot pavement in Arizona at 52°C (125.6°F) and & ≈ 0.84 rate in W rate in Btu/h W Btu/h (b) a hood of a car at 44°C (111.2°F) and & ≈ 0.91 rate in W W rate in Btu/h Btu/h (c) a sunbather at 38°C (100.4°F) and & ≈ 0.91 rate in W W rate in Btu/h Btu/h