ENPH/PHYS 242 – Fall 2014 Problem Set 10 Due Friday November 21, 9:20 am 1. Balmer Formula The Balmer formula describes the emission spectrum of hydrogen as a function of two integer parameters and . Find all allowed combinations of these parameters that describe photons in the visible range (400nm – 750nm), calculate the respective wavelengths and show that all other combinations result in wavelengths outside the visible range. 2. Cross section A radioactive source produces gamma rays with an energy of 662k V. This radiation is directed onto a piece of lead. The thickness of the lead is adjusted so that the fraction of gamma rays that penetrate the lead without interaction is equal to exp 1 ; the thickness of the lead is now 7mm (we call this the absorption or attenuation length). The density of lead is 11.34g/cm ; the atomic weight of lead is 207.2 (this means: the average mass of a lead atom is 207.2amu). a) Use Beer’s law to calculate the cross section of662k V photons with lead atoms. b) If we were to view both scattering partners as solid balls, what would the maximum distance be (centre to centre) for an interaction to happen? c) The radioactive source has an activity of 37kBq (that means: it emits 37 10 photons per second). How thick does a lead shield around the source have to be to assure that not more than 10of the original photons are measured per second on the outside? © W. Rau
© Copyright 2024 ExpyDoc
![Advances in the Water Environment in Japan [PDF 610KB]](http://s3.expydoc.com/store/data/003774248_1-27e2577825acb98968009a9ca43f2287-250x500.png)
![Read Our Winter Newsletter! [PDF]](http://s3.expydoc.com/store/data/002819245_1-205c63bdb65edc8cc0bee9503c6f0c4a-250x500.png)
