Question
This quantity is called “direct” if electrons have the same crystal momentum in the upper and lower levels that define it. For 10 points each:
[10m] Insulators have a high value of what quantity, which is the difference between namesake “valence” and “conduction” levels?
ANSWER: band gap [or energy gap; accept direct band gap; prompt on gap]
[10e] A medium-sized band gap characterizes these materials, as they exhibit properties between insulators and conductors.
ANSWER: semiconductors
[10h] Unlike a “transport” gap, a band gap with this name is the energy needed to produce an electron–hole pair that is bound together. This adjective also describes phonons in which two adjacent atoms vibrate in opposite directions, unlike acoustic phonons.
ANSWER: optical [accept optical band gap or optical phonons]
<Physics>
Summary
| 2024 ACF Winter at UC Berkeley | 2024-11-16 | Y | 3 | 23.33 | 100% | 100% | 33% |
| 2024 ACF Winter at Clemson | 2024-11-16 | Y | 8 | 16.25 | 100% | 63% | 0% |
| 2024 ACF Winter at Ohio State | 2024-11-16 | Y | 7 | 12.86 | 100% | 29% | 0% |
| 2024 ACF Winter at Online | 2024-11-16 | Y | 8 | 16.25 | 100% | 63% | 0% |
| 2024 ACF Winter at UBC | 2024-11-16 | Y | 3 | 16.67 | 100% | 67% | 0% |
| 2024 ACF Winter at Central Florida | 2024-11-16 | Y | 4 | 20.00 | 100% | 100% | 0% |
| 2024 ACF Winter at Oxford | 2024-11-16 | Y | 11 | 15.45 | 100% | 36% | 18% |
| 2024 ACF Winter at Brandeis | 2024-11-16 | Y | 10 | 12.00 | 90% | 30% | 0% |
Data
| Amherst A | Bowdoin B | 10 | 10 | 0 | 20 |
| Williams A | Boston University B | 0 | 10 | 0 | 10 |
| Bowdoin A | BU A | 0 | 10 | 0 | 10 |
| Tufts B | Brandeises Brew | 0 | 10 | 0 | 10 |
| Harvard A | Brown A | 10 | 10 | 0 | 20 |
| Tufts A | Carabrandeis | 0 | 10 | 0 | 10 |
| Yale B | Clark A | 0 | 10 | 0 | 10 |
| Diamond Brandeis | A Brandeis Supreme | 0 | 0 | 0 | 0 |
| MIT A | Yale A | 10 | 10 | 0 | 20 |
| Northeastern A | Yale C | 0 | 10 | 0 | 10 |