A sphere with a radius of 5 cm radiates heat like a black body into the surroundings at a temperature of 
.
What is the temperature of the sphere if the heat energy radiated per second is 1000 W?
What is the heat flow density 1 m away from the sphere?
By how much does the heat flow density of a new sphere change if it has half the radius and half the temperature of the previous sphere?
is 
.
.
lower than that of the first sphere.
