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Dr.Eman Zakaria Hegazy Quantum Mechanics and Statistical Thermodynamics Lecture7 Revision 1. Radiation in the ultraviolet region of the electromagnetic spectrum is usually described in terms of wavelength λ, and is given in angstrom units (1 Å = 10-10 m) or nanometer (10-9 m). Calculate ν, and E for ultra violet radiation with λ = 2000 Å. 2. At what wavelength does the maximum in the energydensity distribution function for a blackbody occur if (a) T=300 K? (b) T=3000K? 3. Using the values of k, h and c , calculate the value of the Stefan –Boltzmann constant and compare it to the experimental value, 5.670x10-8 J.m-2.k4.s-1.(k=1.38 x10-23 J.K-1, h=6.626x10-34J.s and c= 3x108m.s-1 4. When a clean surface of silver is irradiated with light of wavelength 230nm, the stopping potential of the ejected electrons is found to be 0.80V. Calculate the work function and the threshold frequency of silver. 5. Define : Blackbody radiation, photoelectric effect, emission spectrum, threshold frequency, stopping potential