Black Body Radiation: Wien’s Law, Rayleigh-Jeans, Estimate T of objects, What is Teff? (Ch 3)

Radiative Processes & Transfer | Chapter 3 · Blackbody radiation In this "extended version" lecture we discuss properties of Black-Body radiation. I've included a small part also from an earlier version of intro-course to galaxies & cosmology (on accretion discs). Lecture starts with the spectral shape, the Rayleigh-Jeans and Wien limits, and Wien's displacement law. Then we find frequency-integrated properties, finding values and relations for radiation energy density, flux, and pressure. We also hint toward where "ultra-violet catastrophe" come from (Planck's quantum oscillators treated later during course). Examples: Wien's Displacement Law and estimating temperatures of stars and basic properties of galaxies. What is the effective temperature "Teff"? Teff of stars and accretion discs (for example around black holes). 0:00 Introduction and basic spectral shape of Planck curve 5:04 Rayleigh-Jeans limit 8:22 Wien limit 10:30 Wien's displacement law 15:10 Estimate temperature of stars 18:55 Estimate basic properties of galaxies 21:05 Integrated radiation energy density 32:55 Integrated radiation flux 36:20 Integrated radiation pressure 39:45 What is effective temperature "Teff" for stars? 54:50 "Teff" and luminosity from accretion disc, contrasted to stars #astronomy #astrophysics #physics #education Parts of the video are part of the course: Radiation Processes in Astronomy Lecturer: Prof. Dr. Jon Sundqvist Programmes where I teach it: KU Leuven Bachelor Physics & Master Astronomy & Astrophysics, Hasselt University Bachelor Physics (as video course) I record lectures live and do them on black-board in the hope that it will provide a more authentic feeling of the sort: "we're doing the actual work here and now". So like I keep telling students in the classroom: whenever you discover me doing some error let me know directly; for this channel this means make a comment on the videos. Then we can have a look at it, and thereby learn nicely from each other as we continue to develop our knowledge. Link to "Radiative Transfer and Radiative Processes in Astrophysics: Extended Version" playlist:    • Radiative Processes and Radiative Transfer...   Please subscribe here if you want to stay posted on new videos:    / @jonsundqvist   Here's my group's research home page: https://fys.kuleuven.be/ster/research... Playlist for SUPERSTARS-3D:    • Stars & Stellar Winds: Scientific 3D Simul...   Follow me on linkedin for more updates:   / jon-sundqvist-910969272   For original non-extended course black-board class lectures (2025 version), see also here:    • Radiation Processes in Astronomy