For questions 7 and 8, note that stars are nearly perfect radiators (nearly trit
ID: 1397246 • Letter: F
Question
For questions 7 and 8, note that stars are nearly perfect radiators (nearly trite black bodies with emissivity of approximately 1.0) and they are almost perfectly spherical. 7. Sun spots are regions in the Sun?s photosphere that appear dark because they emit less radiation, per unit area, than average. They are dimmer because they are cooler than most of the Sun's surface. Suppose the average temperature of the Sun?s photosphere is 5780 K. If a particular sun spot is only 10% as bright as the normal, bright regions of the Sun?s surface, what is the temperature of the sun spot?Explanation / Answer
from stefans law
the energy emitted per unit area per unit time is proportional
to fourth power of the absolute temperatue
let H1 be the energy emitted by the spot
H2 be the energy emitted by the sun's photosphere
H1 = 10%of H2 = 0.1H2
H1 / H2 = T1^4/T2^4
0.1 = T1^4/5780^4
T1 = 3250.33 k <---------answer