Tuesday, Feb 26, 2008

Collected RA 15.1. Graded it while students finished watching the Hewitt video on Heat Transfer.

Demonstrated the wax brightness lab and showed how to do calculations. Described the lab to calculate the power output of the Sun which we will do the next bright sunny day.

Reviewed with class conduction, convection, and radiation. Gave examples of convection and how it affects onshore and offshore winds.

Introduced Wien's Law and the Stefan-Boltzmann Law. Showed how to use Wien's Law to get the wavelength of maximum emission. Used the Stefan-Boltzmann Law to show how the Intensity vs Wavelength curve various with temperature. At higher temperatures the wavelength of maximum emission shifts towards shorter wavelengths but an object at higher temperature emits more radiation at all wavelengths.

Discussed colors of stars and showed the Intensity (W/m^3) vs wavelength curves for various temperature stars.

Calculated the wavelength of maximum emission for a human. Showed how to calculate the power radiated by a human assuming emissivity = 1.

Talked briefly about the concept of a black body which is an object that absorbs at all wavelengths and emits at all wavelengths. Stars can be approximated as black bodies.

Heat Capacity Lab due tomorrow.