Class 8 & Discussion 4,  2/1/05

Class 8, Highlights
We discussed the important concepts in Chpt 6 of  TB1, that are needed for HW5.
* Light is a electromagnetic wave.
* A pure wave is specific by its wave length, denoted by the Greek letter lambda, and by its frequency, denoted by the Greek letter nu (TB1 uses the letter f, however, all physicist uses nu.)
    ** velocity of a wave = wavelength x frequency.
    ** for light, c = wavelength x frequency, so high frequency light has shorter wavelength.
* Light also behaves like a particle, called photon.
* Energy of a photon, E = h nu, where h is the Planck constant, listed on p.a.. So light  with higher the frequency (so shorter wavelength) has higher energy.
* Energy levels of a electron in an atom and their characteristic spectral of light of emission and absorption.
* The spectra of light emitted or absorbed from the hydrogen atom is very important for astronomical observations.
* Third Law of Thermodynamic: There is the absolute lowest temperature, which we call the absolute zero temperature.
*  We defined temperature in K, Kelvin, and its relation to temperature in C.
* We discussed p.162 of TB2, which has
    ** the Planck distribution, Fig. 6.13,
    ** the Stefan-Boltzmann law, Math Insight 6.2,
    ** Wien's law, Math Insight 6.2.
* We discussed Doppler effects of light (see p. 166 of TB1, Math Insight 6.3), and sound; and showed animations.
* The Doppler shift effect on light from hydrogen, due to the expansion of the universe, provides a way for astronomers to look back in time of the universe.
* We viewed and discussed Fig. 7.20. It shows what types of light can penetrate the Earth atmosphere and what types can not.
* We added the definition of angstrom to p. A-2.

Discussion 4, Highlights
*  Distributed HW5.
* Distributed  Draft Format of Quiz 1.
* Reviewed for Quiz 1
    ** Log_10 plot.
    ** unit conversion, using 1.
    ** density, e.g.
        *** number of pearls/length.
        *** mass/volume.



   


Class 8, Preview
* We will discuss the following reading assignments and HW5. Please have a full first reading of the assignments.
     · p.152 - 171, Chpt 6 of  TB1 , Light: The Cosmic Messenger; 
     · p.85 - 131, Chpt 4 of TB2: Microscopic Weirdness .
* Will hand out and discuss HW5.
* Will hand out Draft Format of Quiz1

Discussion 4, Preview
* Will discuss HW5 further.
* Will review for Quiz 1.