What Makes Radiation Significant?

[Leo Liu]

Homework Statement

It is a question from 2000 SIN exam, the solution does not make sense to me. I would like to know if someone can explain it, many thanks!

Relevant Equations

P=AT^4

 

[berkeman]

Welcome to the PF.

How would you approach the problem? We need you to show your efforts before we can offer tutorial assistance.

 

[haruspex]

It would help if you could indicate what part is not making sense to you.
Do you understand that the received power is FA sin(θ)?
Do you understand that if the absolute temperature is T then the emitted power is 2AσT⁴?
Do you understand that the two will be equal in steady state?

 

[Leo Liu]

Welcome to the PF.

How would you approach the problem? We need you to show your efforts before we can offer tutorial assistance.

Sorry. Since I am a secondary school student, I am unfamiliar with this question. Now I undserstand that the equation on the exam was wrong, thank you very much.

 

[Leo Liu]

It would help if you could indicate what part is not making sense to you.
Do you understand that the received power is FA sin(θ)?
Do you understand that if the absolute temperature is T then the emitted power is 2AσT⁴?
Do you understand that the two will be equal in steady state?

I find out the equation was incorrect, thank you and have a good day.

 

[haruspex]

I find out the equation was incorrect, thank you and have a good day.

In what way? It looks right to me. Who says it is wrong?

 

[Leo Liu]

In what way? It looks right to me. Who says it is wrong?

 

[haruspex]

View attachment 242264

Ah, that equation. I thought you meant the one in the answer.

If you look carefully at the way it is printed you will see there is a suspicious extra blank between the A and the T, and again in "constant =". Seems the text went through a processing stage that couldn't handle Greek characters. Likewise, none of the superscripting works.

Watch out for the same errors in the other questions.