Lecture 10:Radiation
Lecture 10: Radiation
Introduction 目 Definition:energy emitted by matter that is at an infinite temperature Nature of thermal radiation ■ all matters radiate it is dependent on the temperature and nature of the material The Electromagnetic Spectrum
Introduction Definition: energy emitted by matter that is at an infinite temperature Nature of thermal radiation all matters radiate it is dependent on the temperature and nature of the material The Electromagnetic Spectrum
X Rays Microwave Gamma rays hermal radiation L 105 104 10-3 10-2 101 10 102 103 10 2(4m) FIGURE 12.3 Spectrum of electromagnetic radiation
Frequency and wavelength of the electromagnetic waves V=c/λ Transparent,semitransparent,and opaque materials Two features:spectral and directional distribution
Frequency and wavelength of the electromagnetic waves Transparent, semitransparent, and opaque materials Two features: spectral and directional distribution ν = c / λ
Blackbody Radiation ▣An ideal surface Absorbs all incoming radiation; Emits the maximum radiation at the same temp. No reflection,no transmission Radiation independent of direction: diffuse emitter
Blackbody Radiation An ideal surface Absorbs all incoming radiation; Emits the maximum radiation at the same temp. No reflection, no transmission Radiation independent of direction: diffuse emitter