The Doppler Effect · 多普勒效应
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| Doppler effect/ˈdɒplə ɪˈfekt/ | 多普勒效应 | duō pǔ lè xiào yìng |
A siren drops in pitch the instant it passes you
- An ambulance races toward you with a high-pitched wail, then drops to a lower pitch as it passes.
- The siren itself never changes — the motion shifts the pitch you hear.
- This is the Doppler effect 多普勒效应: motion changes the observed frequency of a wave.
- It works for sound, light and every kind of wave.
警笛在经过你的那一刻音调骤降
- 救护车鸣着高亢的警笛冲向你,经过时音调降到更低。
- 警笛本身从未改变——是运动改变了你听到的音调。
- 这就是多普勒效应:运动改变一道波被观察到的频率。
- 它对声、光和每一种波都成立。
Why the pitch shifts
- As a source moves toward you, each wave is emitted a little closer, so the waves bunch up.
- Bunched waves have a shorter wavelength and a higher frequency — a higher pitch.
- As it moves away, the waves stretch out — longer wavelength, lower frequency.
- The source's frequency is unchanged; only the observed frequency shifts.
音调为何改变
- 当波源朝你运动时,每一道波都在稍近处发出,所以波挤到一起。
- 挤在一起的波有更短的波长和更高的频率——更高的音调。
- 当它远离时,波被拉开——更长的波长、更低的频率。
- 波源的频率不变;只有被观察到的频率改变。
Move the source · 移动波源
Increase the source's speed and see the waves bunch up ahead and stretch out behind. · 增加波源速度，观察前方波纹密集、后方稀疏的现象。
Toward = higher, away = lower
- Approaching: higher observed frequency (higher pitch, or light shifted toward blue).
- Receding: lower observed frequency (lower pitch, or light shifted toward red).
- The faster the motion, the bigger the shift.
- It happens whether the source moves, the observer moves, or both.
靠近 = 更高,远离 = 更低
- 靠近:观察到的频率更高(音调更高,或光偏向蓝)。
- 远离:观察到的频率更低(音调更低,或光偏向红)。
- 运动越快,偏移越大。
- 无论是波源运动、观察者运动,还是两者都动,它都发生。
A siren moves toward you. Compared with its true note, you hear a: · 一声笛声向你靠近。与你听到的真实音调相比，你听到的是：
Approaching bunches the waves, giving a higher observed frequency (higher pitch). · 接近时波纹被压缩，导致观测频率升高（音调变高）。
As a wave source moves away from you, the wavelength you observe is: · 当波源远离你时，你观测到的波长：
Receding stretches the waves — a longer wavelength and lower frequency. · 退行拉伸了波纹——波长变长且频率降低。
The Doppler effect happens whether the source moves, the observer moves, or both. · 无论波源移动、观察者移动还是两者都动，都会产生多普勒效应。
Relative motion between source and observer produces the shift. · 波源与观察者之间的相对运动导致了这种偏移。
Doppler in the universe
- Light from galaxies moving away is shifted to lower frequency — the famous redshift.
- This is key evidence that the universe is expanding.
- Doppler radar tracks storms and speeding cars by the shift in reflected waves.
- The same simple idea spans a passing siren and the edge of the cosmos.
宇宙中的多普勒
- 远离我们的星系发出的光偏向更低频率——著名的红移。
- 这是宇宙正在膨胀的关键证据。
- 多普勒雷达通过反射波的偏移来追踪风暴和超速汽车。
- 同一个简单的概念,跨越一辆经过的警车到宇宙的边缘。
In the Doppler effect, the source's own frequency changes as it moves. · 在多普勒效应中，波源自身的频率随运动而改变。
The source's frequency is unchanged; only the observed frequency shifts. · 波源频率不变；仅观测频率发生偏移。
Light from a galaxy moving away is shifted toward lower frequency — a ____. · 远离我们的星系发出的光向低频偏移——这是一种 ____。
Receding light lowers in frequency: a redshift, evidence of an expanding universe. · 退行光的频率降低：即红移，这是宇宙膨胀的证据。
Select all · 所有 true statements about the Doppler effect. · 选择关于多普勒效应的所有正确陈述。
Approach = higher, recede = lower, and it explains redshift. The source frequency itself is unchanged. · 接近=频率升高，退行=频率降低，并解释红移。波源自身频率不变。
In the Doppler effect the source's frequency never changes — only the frequency you observe does. Approaching raises it (blueshift for light); receding lowers it (redshift). Don't say the siren "changes its note" — your received frequency changes.
在多普勒效应中,波源的频率从不改变——只有你观察到的频率改变。靠近升高它(光的蓝移);远离降低它(红移)。别说警笛"改变了它的音符"——是你接收到的频率改变了。
A train sounds its horn as it speeds toward, then away from, a listener on the platform.
- Approaching: the listener hears a higher pitch than the true horn note.
- Receding: they hear a lower pitch. The drop happens as the train passes.
一列火车朝站台上的听者疾驰而来,然后远去,一路鸣笛。
- 靠近:听者听到比真实笛声更高的音调。
- 远离:他们听到更低的音调。骤降发生在火车经过时。
The Doppler effect: motion shifts the observed frequency of a wave. A source moving toward you bunches its waves (higher frequency/pitch, blueshift); moving away stretches them (lower frequency, redshift). The source's own frequency is unchanged. Redshift shows the universe is expanding.
多普勒效应:运动改变一道波被观察到的频率。朝你运动的波源使它的波挤在一起(更高频率/音调,蓝移);远离则拉开它们(更低频率,红移)。波源自身的频率不变。红移表明宇宙在膨胀。