Waves and optics
| English | 中文 | Pinyin |
|---|---|---|
| diffraction/dɪˈfrækʃn/ | 衍射 | yǎn shè |
| coherence/kəʊˈhɪərəns/ | 相干性 | xiāng gān xìng |
A decision before an answer
- Two individually bright waves can cancel at a point if their phases oppose.
- Your goal: Analyse wave superposition and interference.
Read the relationship
- Add wave amplitudes, then calculate intensity. Intensity is proportional to squared amplitude for the same medium.
- Use diffraction, polarisation and optical imaging.
Doubling wavelength at fixed slit width makes the first minimum angle:
sin θ=λ/a increases.
Use the defining rule
- A path difference gives phase difference 2πΔ/λ. Coherent sources need stable relative phase.
- Relate phase, frequency and dispersion.
An ideal polariser transmits unpolarised intensity I as:
Averaging the squared projection gives half.
Check the conditions
- For a single slit, minima satisfy a sin θ=mλ for nonzero integers m. A double slit has a different interference condition.
- Relate phase, frequency and dispersion.
Two equal coherent waves have amplitude A each. In phase, their total amplitude is 2A and intensity is 4I₀. With phase difference π, amplitude and ideal intensity are zero. Adding intensities directly misses interference.
For frequency 5 Hz and wavelength 2 m, wave speed is ____ m/s.
v=fλ=5×2=10.
Apply the task format
- Geometric optics needs a stated sign convention. Wave effects matter when apertures are comparable to wavelength.
- Relate phase, frequency and dispersion.
The central single-slit maximum is not obtained by setting m=0 in the minima condition.
Which answer fits this case?
Analyse wave superposition and interference
Wave intensities can always be added without considering phase.
Coherent waves interfere through amplitude addition.
Keep the distinctions
- coherence 相干性 — A stable phase relationship between waves.
- diffraction 衍射 — Wave spreading and interference caused by an aperture or obstacle.
- Analyse wave superposition and interference.
- Use diffraction, polarisation and optical imaging.
- Relate phase, frequency and dispersion.
Match each term with its precise meaning in this lesson.
Keep the distinctions stated in the teaching example.
Put this lesson’s reasoning or event sequence in order.
The order follows the stated process; check each stage before the next.