Modelo ondulatorio
Diploma del Bachillerato Internacional · IB Diploma · Physics · HL Tema 12 3:58 Narración en inglés · Subtítulos en inglés + 中文 quemados en pantalla
Capítulos
Transcripción
A wave can carry energy across water while a floating marker mainly oscillates.
波可以携带能量穿过水面，而漂浮的标记物主要是在原地振荡。
Energy transfer and bulk transfer of matter are different.
能量的传递与物质的整体迁移是不同的。
Frequency is oscillations per time.
频率是单位时间内的振荡次数。
Wavelength is the distance between successive points in phase.
波长是相邻同相点之间的距离。
Wave speed equals frequency multiplied by wavelength.
波速等于频率乘以波长。
Transverse oscillations are perpendicular to propagation.
横波振荡方向与传播方向垂直。
Wavelength is the distance between successive points in phase.
波长是相邻同相点之间的距离。
Frequency is the number of oscillations per unit time.
频率是单位时间内的振荡次数。
At a boundary, frequency stays fixed by the source.
在边界处，频率由波源决定且保持不变。
A change of speed changes wavelength.
波速的变化会导致波长的改变。
Refraction follows from speed differences; angles are measured from the normal.
折射现象源于波速的差异；角度均从法线开始测量。
In the lab: Measure several wavelengths and divide to reduce fractional reading uncertainty.
在实验室中，测量多个波长并取平均值，以降低读数相对不确定度。
Use a ray box with a normal drawn at the boundary.
使用带有边界处法线的光源盒。
Keep the beam away from eyes and record incident and refracted angles clearly.
确保光束远离眼睛，并清晰记录入射角和折射角。
Known: frequency 5 Hz and wavelength 0.40 m.
已知：频率为 5 Hz，波长为 0.40 m。
Use v equals f lambda.
使用公式 v = fλ。
v equals 5 times 0.40, which is 2.0 metres per second.
v = 5 × 0.40 = 2.0 米每秒。
If speed falls to 1.5 metres per second at the same frequency, wavelength equals v divided by f, which is 1.5 divided by 5, equaling 0.30 m.
若频率不变而速度降至 1.5 米每秒，则波长 = v/f = 1.5/5 = 0.30 m。
Your turn: Frequency is 8 Hz and wavelength is 0.25 m.
轮到你了。 频率为8赫兹，波长为0.25米。
Find wave speed.
求波速。
Pause the video and work it out.
请暂停视频，自己算一算。
Check: 8 hertz times 0.25 metres is 2.0 metres per second.
核对：8 赫兹 × 0.25 米，波速为每秒 2.0 米。
The wave frequency does not change simply because the medium changes.
波频不会因介质改变而改变。
A longitudinal wave has oscillations parallel to propagation.
纵波的振动方向与传播方向平行。
Not true that wave frequency always changes when a wave enters a new medium.
不正确。 波进入新介质时，频率并非总是改变。
Frequency is fixed by the source, so it stays the same across a boundary.
频率由波源决定，因此在界面两侧保持不变。
What changes is speed, and therefore wavelength, through v equals f times wavelength.
发生变化的是波速，进而导致波长改变，依据公式v等于f乘以波长。
Frequency is oscillations per time.
频率是单位时间内的振动次数。
Wavelength is the distance between successive points in phase.
波长是相邻同相点之间的距离。
At a boundary, frequency stays fixed by the source.
在边界处，频率由波源决定并保持不变。
Watch for this: the wave frequency does not change simply because the medium changes.
请注意：波的频率不会仅仅因为介质改变而发生变化。
Frequency is 9 Hz and wavelength is 0.80 m.
频率为9赫兹，波长为0.80米。
Find the wave speed.
求波速。
If the speed becomes 5.4 metres per second at a boundary, find the new wavelength.
若波在边界处速度变为5.4米每秒，求新的波长。
Frequency stays the same.
频率保持不变。
The result is a wave speed of 7.2 metres per second; at the boundary the frequency stays 9 hertz, so the new wavelength is 0.60 metres.
结果是波速为每秒7.2米；在界面处频率仍为9赫兹，所以新的波长为0.60米。
Along the wave, one complete cycle from crest to next crest is one wavelength.
沿着波，从一个波峰到下一个波峰的完整周期就是一个波长。
The wave speed equals frequency times wavelength.
波速等于频率乘以波长。
A 5 Hz wave crosses a stationary boundary where speed falls from 2 to 1 m/s.
一个5赫兹的波穿过静止边界，速度从2米每秒降至1米每秒。
Compare wavelengths and frequency.
比较波长和频率。
Explain the unchanged frequency.
解释频率保持不变的原因。
Wavelengths are 0.40 and 0.20 m; frequency remains 5 Hz because the boundary is driven by the same source.
波长分别为0.40和0.20米。 频率保持为5赫兹，因为边界由同一波源驱动。
Moving boundaries require a different analysis.
移动边界需要不同的分析方法。
Pause and check yourself. Explain each point on screen in your own words, then change one number in the last example and say which assumption must still hold.
暂停一下，自我检查：用自己的话解释屏幕上的每个要点，再改动最后一个例子中的一个数字，说明哪个假设仍然必须成立。