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دبلومة البكالوريا الدولية · IB Diploma · Physics · SL الموضوع 12 4:11 سرد باللغة الإنجليزية · ترجمة مدمجة بالإنجليزية + الصينية
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النص الصوتي
A recognizable spectral line appears at a longer wavelength in a distant source.
遥远天体中可识别的光谱线出现在更长的波长处。
Its shift can provide evidence of recession along the line of sight.
其红移可提供沿视线方向退行的证据。
Relative source-observer motion changes observed frequency or wavelength.
相对源与观测者的运动改变观测频率或波长。
For light at a relative speed much smaller than c, the magnitude of the fractional wavelength shift is approximately v over c.
对于相对于光速c小得多的速度，分数波长的变化量级近似为v除以c。
Recession corresponds to longer wavelength, and approach to shorter wavelength.
退行对应更长的波长，接近对应更短的波长。
Redshift: Shift of an identified line toward longer wavelength.
红移：已识别谱线向更长波长方向的移动。
Rest wavelength: Wavelength of the line measured with no relative source motion.
静止波长：无相对源运动时测得的谱线波长。
Compare an identified spectral line with its laboratory rest wavelength.
将已识别的光谱线与实验室静止波长进行比较。
Use z equals observed minus rest, all over rest.
使用公式 z 等于观测值减去静止值，再除以静止值。
Then v is approximately c times z in the stated low-speed model.
然后在所述低速模型中，v 约等于 c 乘以 z。
Do not apply this approximation without checking the regime or treating a cosmological redshift as a simple exact velocity.
在检查适用范围之前，不要应用此近似，也不要将宇宙学红移简单视为精确速度。
In the lab: Use attributed spectra with calibration and line identification.
在实验室中，使用经标定和谱线识别的归属光谱。
Compare several lines for a consistent shift.
比较多条谱线以确认一致的移动。
State uncertainty and distinguish relative line-of-sight motion from an unmeasured transverse component.
说明不确定度，并区分相对视线运动与未测量的横向分量。
Known: a 500 nm rest line is observed at 501 nm.
已知：一条 500 nm 的静止谱线在 501 nm 处被观测到。
z equals 501 minus 500, all over 500, which equals 0.002.
z 等于 501 减 500，除以 500，即 0.002。
With c equals 3.0 times 10 to the 8th m/s, v approximately 6.0 times 10 to the 5th m/s away.
取光速 c 为 3.0×10⁸ m/s，则速度 v 约为 6.0×10⁵ m/s，方向远离。
The sound source denominator formula is not the required SL light approximation.
声源分母公式并非本题所需的 SL 光近似式。
Your turn.
轮到你了。
A 600 nanometre rest line is observed at 601.2 nanometres.
一条静止波长为 600 纳米的谱线在 601.2 纳米处被观测到。
Find z, the observed wavelength minus the rest wavelength, divided by the rest wavelength.
求 z，即观测波长减去静止波长，再除以静止波长。
The approximate shift relation does not show that light travels faster from an approaching source.
近似位移关系并不能表明来自接近光源的光传播得更快。
A single unidentified line cannot safely establish a redshift.
仅凭一条未识别的谱线，无法安全地确立红移现象。
Not true: An observed redshift means light speed increased.
不正确。 观测到的红移并不意味着光速增加了。
Light speed in vacuum is the same for all observers.
真空中光速对所有观察者而言都是相同的。
Redshift is a change in observed wavelength from relative motion (or expanding space), not light travelling faster or slower.
红移是相对运动或空间膨胀导致的观测波长变化，而非光传播速度变快或变慢。
Relative source-observer motion changes observed frequency or wavelength.
相对运动改变观测到的频率或波长。
Compare a identified line with its laboratory rest wavelength.
将识别出的谱线与实验室静止波长进行比较。
Watch for: the approximate shift relation does not show that light travels faster from an approaching source.
请注意：近似位移关系并不表明来自接近光源的光传播速度更快。
A 500 nanometre rest line is observed at 502.5 nanometres.
一条500纳米的静止谱线被观测为502.5纳米。
Find z.
求z。
Redshift does not mean the speed of light increased.
红移并不意味着光速增加了。
The result is a redshift of 0.005.
结果是红移为0.005。
Find a known line, measure how far it has moved, and divide by its rest wavelength to get z.
找到一条已知谱线，测出它移动的距离，再除以静止波长得到z。
At low speed the recession speed is about c times z.
低速时，退行速度约等于光速乘以z。
A 500 nanometre rest line is observed at 499 nanometres.
一条静止波长为 500 纳米的谱线，观测到的波长为 499 纳米。
Find z and the low-speed radial velocity, using c equal to 3 times 10 to the 8 metres per second. Explain the sign and the limit.
取 c 等于 3×10⁸ 米每秒，求 z 和低速近似下的径向速度，并解释符号和适用范围。
z is minus 0.002, so v is about c times z, which is minus 6 times 10 to the 5 metres per second: approaching, under the positive-away convention.
z 等于 −0.002，所以 v 约等于 c 乘以 z，即 −6×10⁵ 米每秒：按“远离为正”的约定，表示正在接近。
This small-z kinematic approximation does not cover every origin of redshift.
这种小 z 的运动学近似并不适用于所有红移来源。
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。