sounds right - obviously you could use the same methods to get the intensity at neptune or any other r that is greater than the sun's radius.(Original post by Danny.L)
Yeah, I showed my teacher my working today, he said it wa great. However I could get the intensity directly via the method you used. He went a step further and showed I1R1^2 = K I2R2^2 = k
therefore they equal each other.
He also spotted what I had done wrong for my working by multiplying 1400 Wm-2 by (1.5 *10^11)^2. That was finding the intensity 1m away from the centre of the sun, but we wanted it at the surface, so needed to then divide by (7 * 10*)^2 (which is radius of sun squared). I think that's correct! How does that sound to you?
Is it worth it?