Week 6 Start Feb. 9th
Exam 1---good work. Solutions posted. Average ~82.
Ch. 6 problems ----3,6, 9, 13, 17, and...do the "Colbert problem below" DUE FRIDAY 13 ASSUMING WE GET TO NEEDED MATERIAL.
Given the temperature of the universe is 2.7K (microwave background from big
bang). This is assigned problem ----find M(photonic) of universe?
a) What is the Intensity (power per area--but relates to energy density) of light put out by the universe as a
large blackbody
b) Further given that I(total)=c/4*(Energy density), determine
the photonic energy density just due to the background emission?
c) Now use the radius of the universe as 18 BILLION LY OR IS IT 13
billion LY to determine the total energy due to the background light, and
determine the corresponding mass equivalent.
Here is a thought for cyop if you wish---make it your own----Take a being (yourself, Klingon, Xindi, Gungan, Dug, Vogon, or other species--Vorlons, ET, Wall-E, Yoda, ) ----and dump them outside the airlock of your spaceship (in deep deepest darkest space). You wish to calculate their initial rate of change of temperature due to radiative heat loss (there is no other heat loss here). You might assume they are in a special spherical space suit, blenderized, and stirred (not shaken) sufficiently to maintain a uniform body temperature. You may further want to assume that we are all mostly sacks of water. You are finding the initial dT/dt. You will need certain initial assumptions. If you wish to go deeper it is possible to find dT/dt in general (solution to diffeq with given assumptions --model building).
YOU are a lightbulb. What is your wattage? (You may need to know the surface area of your skin--please consult with Buffalo Bill/Jame Gumb).
What would your temperature need to be if you were to radiate 1.21 GW of power?
You have a standard incandescent lightbulb. What fraction of the power is emitted in a 1nm range at (around) a wavelength of say 5microns?
You are doing a physics experiment looking at 780nm rubidum light, but get very weak signal and can yield only single photons at a time ever few milliseconds. Unfortunately the experiment must be done at a high termperature in a 700C oven---that you have constructed yourself using space shuttle like heat sheild insulation material (You have no Kyber Crystals). Does your signal get swamped by the background thermal blackbody radiation of the oven containing the Rubidium vapor? You may need to count all photons emitted over the entire solid angle, and then make some assumptions about solid angle subtended by your detector.
Looking ahead. (dates TBA)
Ch 7--problems 1, 2, 7, 9, 15 TBA
Ch. 8 --problems 2,4, 5, 7, 14 (you should ask lots of questions on 14), 17, and 25. TBA
Ch. 9 4, 13, 15, 16, 27 TBA