9. given radius r = 8.21*10^11 m
surface temperature, T = 3500 K
rate of energy radiation from the star = r
now from stefan's law
r = sigma*A*e*T^4
sigma = stefans constat = 5.67*10^-8
A = 4pi*r^2
T = 3500 K
e = 1 ( for a blackbody)
hence
r = 72.069484*10^30 W
hence option a) 7.21*10^31 W
9. The red super-giant star, Betelgeuse, has a radius of8.21xI m. The spherical surface behaves as...
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