Radiation Problem: Black-body Expansion, T_f=xT_i

  • Thread starter Thread starter neelakash
  • Start date Start date
  • Tags Tags
    Radiation
Click For Summary
SUMMARY

The problem involves black-body radiation expanding adiabatically from an initial temperature T_i to a final temperature T_f in a volume that increases from V to 8V. The correct final temperature factor x is determined to be 0.25, not 1, as photons do not interact with each other, and the expansion does not affect their temperature. The Stefan-Boltzmann Law is essential for understanding the energy and entropy relationships in this context, defined as U=bVT^4 and S=(4/3)bVT^3.

PREREQUISITES
  • Understanding of black-body radiation principles
  • Familiarity with the Stefan-Boltzmann Law
  • Knowledge of adiabatic processes in thermodynamics
  • Basic concepts of energy and entropy in thermodynamic systems
NEXT STEPS
  • Study the implications of the Stefan-Boltzmann Law in thermodynamic systems
  • Explore adiabatic expansion processes in detail
  • Learn about the relationship between temperature, volume, and energy in black-body radiation
  • Investigate the derivation and applications of U=bVT^4 and S=(4/3)bVT^3
USEFUL FOR

Students and professionals in physics, particularly those focusing on thermodynamics and radiation, as well as anyone involved in energy transfer and heat exchange studies.

neelakash
Messages
491
Reaction score
1

Homework Statement



Black-body radiation, at temperature Ti fills a volume V. The system expands adiabatically
and reversibly to a volume 8V. The final temperature T_f = xT_i, where the factor x is equal to
(a) 0.5 (b) 2.8 (c) 0.25 (d) 1

Homework Equations


The Attempt at a Solution



Correct answer should be (d)1 because, photons do not feel attraction or repulsion potential to each other.So, increasing volume adiabatically should not reduce or increase its temperature.

Please check if I am correct.
 
Physics news on Phys.org
This is incorrect. The Stefan-Boltzmann Law tells us that the energy and entropy of blackbody radiation in a box are [itex]U=bVT^4[/itex] and [itex]S=\frac{4}{3}bVT^3[/itex], respectively, where [itex]b[/itex] is a constant (reference: Callen's Thermodynamics). I'll leave the rest to you.
 
Last edited:

Similar threads

  • · Replies 12 ·
Replies
12
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
Replies
4
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 7 ·
Replies
7
Views
4K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 4 ·
Replies
4
Views
6K
Replies
7
Views
2K
  • · Replies 6 ·
Replies
6
Views
5K
  • · Replies 1 ·
Replies
1
Views
2K