familiari nf3795 quantum atomic yeazell 58395 1 The energy of one photon is 1 The slower one correct This print out should have 17 questions Multiple choice questions may continue on the next column or page nd all choices before answering 001 10 0 points A helium neon laser emits light of wavelength 632 8 nm and has a power output of 20 mW How many photons are emitted per second by this laser Correct answer 6 37903 10 16 Explanation Let P 20 mW 0 02 W 632 8 nm hc 1240 eV nm and Ephoton hc so the number of photons emitted per second by this laser is n P Ephoton P hc 632 8 nm 0 02 W 1240 eV nm 6 37903 10 16 1 eV 1 6 10 19 J 002 10 0 points You do a photoelectric experiment and you nd two di erent values of the maximum ki netic energy of photoelectrons emitted from a metallic surface when light of two frequencies is incident on the surface of When 7 09167 10 netic energy is 2 10 frequency 7 65626 10 imum kinetic energy is 2 4 10 frequency a Hz is used the maximum ki J When light of a Hz is used the max J light 14 19 19 14 From your rough experiment nd a value for Planck s constant Hint It is related to the slope Correct answer 7 08482 10 34 Js Explanation The kinetic energy of the electron is deter mined by the energy of the photon minus the energy needed to remove the electron from the surface K hf W Note that h is the slope in this function so using the two points we can nd this slope or this experimental measurement of Planck s constant 7 08482 10 m s 34 003 10 0 points One electron travels twice as fast as another Which has longer wavelength 2 More information is needed 3 The two have the same wavelength 4 The faster one Explanation The twice as fast electron has twice the mo mentum By de Broglie s formula wavelength is inversely proportional to momentum so twice the momentum means half the wave length Thus the slower electron has the longer wavelength 004 10 0 points What is the uncertainty in the speed of a proton if it is desired to locate its position to within an uncertainty of x 1 91 nm Planck s constant is 6 63 10 J s and the mass of the proton is 1 67 10 kg 27 34 Correct answer 16 5407 m s Explanation 34 Let h 6 63 10 m 1 67 10 x 1 91 nm 1 91 10 J s kg 27 and 9 m familiari nf3795 quantum atomic yeazell 58395 2 From the Heisenberg uncertainty principle x px x m vx h 4 h 4 vx h 4 m x 6 63 10 34 J s 4 1 67 10 27 kg 1 1 91 10 9 m 16 5407 m s 005 part 1 of 2 10 0 points A hypothetical atom has four energy states as shown V e y g r e n E 00 1 2 3 4 5 6 7 8 n 4 n 3 n 2 n 1 Which of the following photon energies E could NOT be found in the emission spectra of this atom after it has been excited to the n 4 state n 4 n 3 n 2 n 1 1 E 1 eV 2 E 5 eV 3 E 4 eV correct 4 E 2 eV 5 E 3 eV Explanation By subtraction the transition from n 4 to n 3 would release 1 eV from n 4 to n 2 would release 3 eV from n 3 to n 2 would release 2 eV from n 3 to n 1 would release 5 eV The only choice remaining is 4 eV 006 part 2 of 2 10 0 points Which of the following transitions will pro duce the photon with the longest wavelength 1 n 4 to n 3 correct 2 n 4 to n 1 3 n 3 to n 2 4 n 3 to n 1 5 n 2 to n 1 Explanation The longest wavelength is produced in the case where the least amount of energy is released from n 4 to n 3 in this case That is 007 part 1 of 3 10 0 points Consider just four of the energy levels in a certain atom as shown in the diagram below How many spectral lines will result from all possible transitions among these levels Which transition corresponds to the highest frequency light emitted Which transition corresponds to the lowest frequency 1 three level 4 to level 3 transition level 2 to level 1 transition familiari nf3795 quantum atomic yeazell 58395 3 2 three level 2 to level 1 transition level 4 to level 3 transition 3 six level 4 to level 1 transition level 4 to level 3 transition correct 4 three level 4 to level 1 transition level 4 to level 3 transition Explanation Six transitions are possible as shown two frequencies is equal to the frequency of light emitted in the transition from quantum level 4 to the ground state quantum level 1 Because energies are additive so are the frequencies However the wavelength rela tionship is not that simple wavelength is in versely proportional to the frequency so the reciprocals of the wavelengths are additive 1 4 3 1 3 1 1 4 1 009 part 3 of 3 10 0 points Suppose the four energy levels were somehow evenly spaced How many spectral lines would result n 4 n 3 n 2 n 1 The highest frequency transition is from quantum level 4 to level 1 The lowest frequency transition is from quantum level 4 to level 3 4 three correct Explanation Only three 008 part 2 of 3 10 0 points An electron de excites from the fourth quan tum level to the third and then directly to the ground state Two photons are emitted How does the sum of their frequencies com pare to the frequency of the single photon that would be emitted by de excitation from the fourth level directly to the ground state 1 The sum is larger than the frequency of the single photon 2 The sum is smaller than the frequency of the single photon 3 None of these 4 The sum is equal to the frequency of the single photon correct Explanation As shown in the diagram the sum of the The transition from 4 to 3 would involve the same di erence in energy and be indis tinguishable from the transition from 3 to 2 or from 2 to ground Likewise the transition from 4 to 2 would have the same change in energy as a transition from 3 to ground 010 10 0 points A 6 5 g particle is moving with a speed of approximately 0 2 cm s in a box of length 1 514 cm 1 six 2 ve 3 four n 4 n 3 n 2 …