Advice needed: Astronomy radiation problem

[snowflakita78]

Homework Statement

Calculate the flux at point P located at a distance r from the centre of a sphere with uniform brightness, B. Idem for an infinite plane with the same brightness B. And the same for a square surface with side L.

Relevant Equations

N/A

Hi! I’m really struggling to solve the last part of this problem, from where it says “Idem for an infinite plane with the same brightness B. And the same for a square surface with side L.”.

Could anyone please help or point me in the right direction? Thank you so much in advance!

 

[haruspex]

Homework Statement:: Calculate the flux at point P located at a distance r from the centre of a sphere with uniform brightness, B. Idem for an infinite plane with the same brightness B. And the same for a square surface with side L.
Relevant Equations:: N/A

Hi! I’m really struggling to solve the last part of this problem, from where it says “Idem for an infinite plane with the same brightness B. And the same for a square surface with side L.”.

Could anyone please help or point me in the right direction? Thank you so much in advance!

Per forum rules, you must show some attempt.
Can you write a suitable integral?