How to Calculate Time for Temperature Drop in Heat Radiation Problem?

[neelakash]

Homework Statement

A spherical black body having R=0.1m and initial temperature T1=10^3 K is cooled by radiation.The surrounding medium is at a temperature T=0K.What time will it take for the temperature of the sphere to drop to T2=100K?
Given heat capacity is C and density d
The answer is :

(CdR/9σ)(T2^(-3) - T1^(-3))

Homework Equations

The Attempt at a Solution

I think just application of Newton's law of cooling will suffice...Isn't it?

 

[Amith2006]

No, u can't use Newton's law of cooling because the temp. difference is large.
U can use stefan's law.

 

[neelakash]

OK,I missed...
Then how to proceed?