bass (zcb96) - W25 HW3 Bohr - lacker - (Q3 AP) This print-out should have 13 questions. Multiple-choice questions may continue on the next column or

bass (zcb96) – W25 HW3 Bohr – lacker – (Q3 AP) 1 This print-out should have 13 questions.

Multiple-choice questions may continue on the next column or page – nd all choices before answering. 001 10.0 points A surface whose work function is 4 .7 eV is illuminated by a light whose wavelength is 88 .3 nm.

What is the maximum velocity of a photo- electron emitted from the surface? The speed of light is 3 ×108 m /s and Planck’s constant is 6 .63 ×10 34 J·s .

Answer in units of km /s. 002 (part 1 of 2) 10.0 points Molybdenum has a work function of 4 .2 eV.

Find the cuto wavelength for the pho- toelectric e ect. The speed of light is 3 ×10 8 m/s and Planck’s constant is 6 .626 ×10 34 J·s .

Answer in units of nm.

003 (part 2 of 2) 10.0 points Calculate the stopping potential if the inci- dent light has a wavelength of 137 nm. Answer in units of V. 004 10.0 points Photons of wavelength 431 nm are incident on a metal. The most energetic electrons ejected from the metal are bent into a circular arc of radius 18 .2 cm by a magnetic eld with a magnitude of 2 .07 ×10 5 T.

What is the work function of the metal?

The speed of light is 3 ×10 8 m /s and Planck’s constant is 6 .626 ×10 34 J·s .

Answer in units of eV.

005 10.0 points When a photon hits an electron and gives it energy, what happens to the frequency of the photon after bouncing from the electron?

1. The frequency decreases.

2. The frequency increases.

3. The frequency remains the same. 4.

It requires a case-by-case analysis. 006 (part 1 of 3) 10.0 points Consider just four of the energy levels in a certain atom, as shown in the diagram below. n = 1 n = 2 n = 3 n = 4 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. six; level 4 to level 1 transition; level 4 to level 3 transition.

2. three; level 2 to level 1 transition; level 4 to level 3 transition.

3. three; level 4 to level 3 transition; level 2 to level 1 transition.

4. three; level 4 to level 1 transition; level 4 to level 3 transition. 007 (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 smaller than the frequency of the single photon.

2. None of these bass (zcb96) – W25 HW3 Bohr – lacker – (Q3 AP) 2 3. The sum is larger than the frequency of the single photon.

4. The sum is equal to the frequency of the single photon. 008 (part 3 of 3) 10.0 points Suppose the four energy levels were somehow evenly spaced. How many spectral lines would result?

1. three 2. ve 3. six 4. four 009 (part 1 of 2) 10.0 points In the diagram the energy di erence between states Band Cis twice the energy di erence between states Aand B. In a transition from Cto B, an electron emits a photon of wavelength 370 nm. A B C What wavelength is emitted when the pho- ton jumps from Bto A?

Answer in units of nm. 010 (part 2 of 2) 10.0 points What is the emitted wavelength when it jumps from Cto A?

Answer in units of nm. 011 10.0 points If we take as our zero energy as the energy of the state with the electron and proton sep- arated and are at rest, the energy of an H atom in a state characterized by the principal quantum number n= 13. What is the energy of this state? As- sume that the ionization energy of hydrogen is 13 .606 eV.

Answer in units of eV. 012 10.0 points The average kinetic energy of gas atoms corre- spond to the energy di erence E= 10 .2 eV between the ground state and the rst excited state of hydrogen. What would the temperature of H gas have to be? The value of the Boltzmann constant is 1 .38 ×10 23 J/K and 1 eV = 1 .6 × 10 19 J/eV .

Answer in units of K.

013 10.0 points Two hydrogen atoms collide head-on and end up with zero kinetic energy. Each then emits a photon with a wavelength of 141 .8 nm ( n= 2 to n= 1 transition).

At what speed were the atoms moving before the collision? Planck’s constant is 6 .62607 ×10 34 J·s and the speed of light is 3 ×108 m /s.

Answer in units of m /s.