Earth, Sun and Analyzing Starlight Worksheet

Earth, Sun and Analyzing Starlight Worksheet Name Leah Walker Please answer in complete sentences and show all calculations in detail. Part 1: As you recall, Power is defined as energy per unit time, [with SI units: J/s, or Watt (W) ]. Radiative flux (energy flux density) is power emitted (or received) per unit area [with SI units: W/m 2 ]. In Chapter 17 you learned that a star’s luminosity (L) is the total power emitted by the star. Only a fraction of that reaches us here on Earth and the amount of it per unit area we call the apparent brightness . In Chapter 5 you learned that light propagation follows the inverse square law . Apparent brightness can then be expressed as the following: Brightness (or Flux) ¿ L 4 π D 2 where D is the distance from the source to an observer on Earth and L is the luminosity of the source. Calculate the solar flux (solar irradiance) received on Earth, i.e., the apparent brightness of the Sun, given Sun luminosity of L ⊙ = 3.84x10 26 W and distance from Sun to Earth of 1 AU = 1.49x10 11 m. (Note: the calculated number is also referred to as the solar constant) F = (3.84 x 10^26 W) / (4π(1.49 x 10^11 m)²) F = (3.84 x 10^26 W) / (8.84 x 10^23 m²) = 434.5 W/m² 434.5 W/m² How many 100 W light bulbs can you power if you can collect and use 100% of the solar irradiance with a 1 m 2 solar panel? (Just for reference, the solar irradiance at the surface is 25% less since some gets absorbed on its way through the atmosphere. Also, typical solar panels are around 20% efficient currently.) P=(1360W/m2)(1m2)=1360W n= 100W/1360W =13.6≈14 light bulbs. Part 2: In a few sentences describe what we mean by the solar wind? How is Earth’s surface protected from the solar wind?