chem120a_ps1_fa10

# chem120a_ps1_fa10 - emits a photon that has a wavelength of...

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Chem 120A Problem Set 1 Out: Sep. 1, 2010; Due: Sep. 8, 2010 1. a) The mean temperature of the Earth’s surface is 288 K. Calculate the wavelength at the maximum of the Earth’s black body radiation. To what part of the electromagnetic spectrum does this correspond? b) The fireball in a thermonuclear explosion can reach temperatures of approximately 10 7 K. What value of black body λ max does this correspond to? In which region of the electromagnetic spectrum is this wavelength? 2. The power output of a laser is measured in units of Watts (W), where one watt is equal to one joule per second (1 W = 1 J s - 1 ). A helium-neon laser of the type used in supermarket scanners produces 0.5 mW and emits light at 632.8 nm. What is the number of photons emitted per second by this laser? 3. A ground-state hydrogen atom absorbs a photon of light that has a wavelength of 97.2 nm. It then
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Unformatted text preview: emits a photon that has a wavelength of 486 nm. What is the ﬁnal state of the hydrogen atom? 4. Calculate the de Broglie wavelength for a) an electron with kinetic energy 100 eV, b) a proton with kinetic energy 100 eV, and c) an electron in the ﬁrst Bohr orbit of a hydrogen atom. 5. What speed does an O 2 molecule have if it has the same momentum as a photon of wavelength a) 190 nm? b) 0.2 nm? Compare the results with the average speed of an O 2 molecule at T= 300 K, calculated from the rms velocity v rms = p 3 kT / m and comment on the implications of your result for whether quantum effects are important in the translations of molecules at room temperature. Chem 120A, Fall 2010 1...
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