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# p1042.pdf - Chapter 1 he(6.626 x 10*“ J-s(2.998 x 108...

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Unformatted text preview: Chapter 1 he (6.626 x 10*“ J-s) (2.998 x 108 m-s") 2 =2 10"SJ A l x 10“”m X 1—10. Express the Planck distribution law in terms of A (and dA) by using the relationship )tu : c. 87th v3dv We know that vi = c, so dv = ~ch/A2. Substituting, we obtain 87th -C4d)\. MT)!“ = :Tk5(ehc/AkBT _ l) 8nhc dA = A5 eke/MET _ 1 where we have dropped the negative sign for convenience. It occurs because dv and dA have opposite signs. WW 1—11. Calculate the number of photons in a 2.00 mJ light pulse at (a) 1.06 pm, (b) 537 nm, and (c) 266 nm. _ (6.626 x 10*34 J.s)(2.99s x 108 ms") " 1.06 x 10’6 m = 1.87 x 10"“‘1—photon"l Since 2.00 m1 of energy are contained in the light pulse, 2.00 x 10"3 J Number of photons = “ﬁg-“~113- 1.87 x 10‘ J>photon = 1.07 x 1016 photons Parts (b) and (c) are done in the same manner to find b. 5.41 x 1015 photons c. 2.68 x 10'5 photons he mean temperature of the Earth’s surface is 288 K. Calculate the wavelength at the maximum of he Earth’s blackbody radiation. What part of the spectrum does this wavelength correspond to? From Equation 1.4, A _ 2.90 x10“3 m-K W ““ 288 K This is in the infrared region of the spectrum. 2 1.01 x 10*5 m W 143. A helium—neon laser (used in supermarket scanners) emits light at 632.8 nm. Calculate the frequency of this light. What is the energy of a photon generated by this laser? .mmawm ..«.mwmmwwmmmwwmWWW.ismm.mWMmwwmmmwwwwmeMwmmemmaWawmaasmmwmwmaamwmmemmWaawmmsmmwmmmmmwsammmmmqmsmswam/«mewMamammz ...
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