Midterm 2 topic guide
Waves (2.2)
-
- Features of a wave (amplitude, wavelength, speed, restoring force, wave speed, motion of wave vs. medium)
- Types of waves (transverse, compression)
- Kinds of common waves
- How waves add
- Diffraction
- Interference
Moving like a wave and hitting like a particle (3.2)
-
- Double slit experiment
- Big interferometer (including blocking of arms)
- Effects of color (stripe spacing, how hard photons/particles hit)*
- Single photon limit (pointillism paintings, blocking of paths, stripe spacing, strength of photon hits, interpretation of a single particle's path)*
- "Moves like a wave and hits like a particle"
- Electrons, neutrons, molecules (how they behave in a double slit or interferometer)
History of computation (5.2)
-
- Idea that computers are devices, no inherent understanding
- Rough timeline of computational history
World is made of notes (7.1)
-
- Length of a ripple
- How to measure with a variable arm-length interferometer
- How bandwidth (color range) relates to ripple length*
- Details of changing color vs. changing range of color on ripple length
- How bandwidth relates to speed one can send information
- Why one buys bandwidth, spectrum allocation
- Particle introverts and extroverts*
- He3 & He4 experiment, explaining how it works
Looking at the sky (7.2)
-
- How waves add (walking on the beach metaphor)*
- How this changes with distance along the beach
- How this changes with distance between sources
- How resolution depends on telescope size
- Why interferometers can have high resolution (shards of a much larger telescope)
- Where does a photon enter a telescope
- Hanbury Brown & Twiss
- Applications of interferometers
- How waves add (walking on the beach metaphor)*
Catching waves (8.1, 8.2)
-
- Trapped waves (Guitar strings, drum heads, fundamental, harmonics, notes/colors, how they depend on the size of the trap, etc.)*
- Electron waves in a quantum corral
- Electron waves in an atom
- Spectra, and how the colors we see are related to the electron waves*
- How quantum dots work, why they have different colors
"Fun" essay question examples:
- Describe how bandwidth (color range) relates to the length of a particle ripple, and how this is related to spectrum allocation. [Key ideas: ripple length and color range; central color; bunching of light; bandwidth; spectrum allocation.]
- In a classic experiment milliKelvin He atoms were dropped onto a sensor. If the Helium was isotope He4 bunching was observed, if isotope He3 was used anti-bunching was seen. Explain these results using the ideas of particle ripples. [Key ideas: size of a particle ripple; extroverts and introverts; packing fermions to act like bosons.]
- Explain why larger telescopes have better resolving power. [Key ideas: width of a particle ripple; how ripples from sources overlap (e.g. beach metaphor); what is needed to separate light from different sources.]
- Starting with analogy of waves on a guitar string, explain the discrete spectra seen from atoms. [Key ideas: specific energy waves in a trap (fundamental, first harmonic, etc.); electron waves in an atom; energy of light is difference in electron wave energy; color of light is given by energy.]
- Explain how quantum dots work. [Key ideas: specific energy waves in a trap (fundamental, first harmonic, etc.); how energy of wave depends on trap size; electron wave in a quantum dot; how color of quantum dot is related to their size.]