Download presentation
Presentation is loading. Please wait.
1
The Laws of Thermodynamics
Zeroth law First law: Energy conservation Third law Second law
2
Other Results from Thermodynamics
Equipartition Degrees of Freedom Stefan-Boltzmann Law Wien’s Displacement Law Phase Diagrams l Tmax = const.
3
Quasi-static processes
Quasi-static processes: near equilibrium States, initial state, final state, intermediate state: p, V & T well defined Sufficiently slow processes = any intermediate state can be considered as at thermal equilibrium. Criterion: It makes sense to define a temperature (ie) there is a statistical average Examples of quasi-static processes: - iso-thermal: T = constant - iso-volumetric: V = constant - iso-baric: P = constant - adiabatic: Q = 0
4
State functions a b c a. isovolumetric b. isobaric a. isobaric
b. isovolumetric isothermal the work done by a system depends on the initial and final states and on the path it is not a state function. energy transfer by heat also depends on the initial, final, and intermediate states it is not a state function either.
5
Summary Thermodynamics is just an equilibrium theory.
But natural processes are usually not in eq. and irreversible. Kinetic theory; statistical mechanics Summary Quasi-static process Character isovolumetric V = constant isobaric P = constant isothermal T = constant adiabatic
6
Blackbody Radiation Spectral energy density of a black body
8
Test Plot: Planck formula vs. Wien, Rayleigh
9
Source Wikipedia
10
BBD Theory EM field in a box as superposition of standing waves
Planck: quantize as n* hf Planck Distribution Modes with hf>>kT are exponentially suppressed
11
Summing over modes in 3d for photons The spectrum of the photons
12
Best confirmation: Cosmic Background Radiation
Summing over all frequencies gives the total energy (the Gaussian integral yields pi^4/15) Best confirmation: Cosmic Background Radiation
13
Fitting solar radiation by BBD
14
X-Ray diffraction
15
Bragg’s law:
16
14 Spatial Lattices
17
Visualizing Cubic Lattices
18
Symmetry in Cubic Lattices
19
Hexagonal lattices
20
Miller Indices ~ describing planes
in 3d Lattices
23
Reciprocal Lattice
24
Brillouin Zones and Wigner Seitz cells
25
Reciprocal lattice Diffraction pattern
26
Spectral lines and Symmetry
27
X-Ray Spectra ~ Interpretation
28
Powder Spectra
29
X-rays, practical issues
Rev Sci Instr 3/1939
30
Microwave Radiation, Microwave Horns
J Singal et al. Typical microwave triode design
31
Horn Gain fct of angle Reflection loss horn
32
Theory of EM Horns 1939, reprinted 2006
33
Pyramidal horns, optimal dimensions
Horn antenna types, wikipedia John Kraus ‘Antennas’
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.