Question

6 -19 points 1M14 8.2.017 My Notes Suppose a hypothetical object has just four quantum states, with the following energies: -0.6 eV (third excited state) 1.4 eV (second excited state) 2.8 eV (first excited state) 5 eV (ground state) (a) Suppose that material containing many such objects is hit with a beam of energetic electrons that ensures that there are always some objects in all of these states. What are the six energies of photons that could be strongly emitted by the material? (In actual quantum objects there are often "selection rules" that forbid certain emissions even though there is enough energy; assume that there are no such restrictions here.) List the photon emission energies in order from largest to smallest. If two different transitions would praduce photons of the same energy, list that energy twice ev (largest) ev ev ev ev ev (smallest) (b) Next, suppose that the beam of electrons is shut off so that all of the objects are in the ground state almost all the time. If electromagnetic radiation with a wide range of energies is passed through the material, what wil be the three energies of photons corresponding to missing ("dark") lines in the spectrum? Remember that there is hardly any absorption from exited states, because emission from an excited state happens very quickly, so there is never a significant number of objects in an excited state. Assume that the detector is sensitive to a wide range of photon energies, not just energies in the visible region. Ust the dark-line energies in order from largest to smallest. eV (largest) ev eV (smallest) Additional Materials Section 8.2

Answer 1

a) Order is largest to smallest Largest energy for photon is, LE-E3-E 4.4 eV Smallest energy for photon: SE-E3-E. -0.8 eV Mid energies of photon: AE -E -E - 2.2 eV AE-E,-E -3.6 eV 2.2 eV Answer: Largest to smallest 4.4 eV 3.6 eV 2.2 eV 2.2 eV 14 eV 0.8 eV

b) Electromagnetic radiations corresponding to the missing lines in the spectrum are Smallest energy is, 2.2 eV Middle energy is 3.6 ev Largest energy is, 4.4 eV Answer: Largest to smallest: 4.4 eV 3.6 eV 2.2 eV