Double-Slit Interference and Diffraction Gratings · 双缝干涉与衍射光栅
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| diffraction grating/dɪˈfrækʃn ˈɡreɪtɪŋ/ | 衍射光栅 | yǎn shè guāng shān |
Shine light through two slits — and get stripes, not two lines
- Send light through two narrow slits and the screen shows a row of bright and dark stripes.
- Not two bright lines as you'd expect — an interference pattern.
- This is Young's double-slit experiment, and it proved light is a wave.
- The same idea, with thousands of slits, becomes a diffraction grating.
让光穿过两条缝——得到条纹,而非两条线
- 让光穿过两条窄缝,屏幕上显示出一排明暗条纹。
- 不是你预期的两条亮线——而是一个干涉图样。
- 这就是杨氏双缝实验,它证明了光是波。
- 同样的概念,用上千条缝,就成了衍射光栅。
How the fringes form
- Light spreads (diffracts) from each slit, and the two sets of waves overlap and interfere.
- Where they arrive in phase, they add — a bright fringe.
- Where they arrive out of phase, they cancel — a dark fringe.
- The pattern is a direct picture of constructive and destructive interference.
条纹如何形成
- 光从每条缝散开(衍射),两组波重叠并干涉。
- 它们同相到达处,相加——一条亮纹。
- 它们反相到达处,相消——一条暗纹。
- 这个图样是相长和相消干涉的直接写照。
Two waves interfering · 两列波发生干涉
Change the phase difference and watch two waves add to bright (in phase) or cancel to dark (out of phase). · 改变相位差，观察两列波如何叠加成亮纹（同相）或抵消成暗纹（反相）。
The double-slit interference pattern is evidence that light is a: · 双缝干涉图样是光为以下哪种性质的证据：
Interference is a wave phenomenon, so the fringes prove light is a wave. · 干涉是波动现象，因此条纹证明光是波。
The bright-fringe condition
- Bright fringes appear where the path difference from the two slits is a whole number of wavelengths.
- The condition is $d\sin\theta = m\lambda$, with $m = 0, 1, 2, \ldots$
- Closer slits (smaller $d$) or a longer wavelength spread the fringes further apart.
- Measuring the fringe spacing lets you calculate the wavelength of the light.
亮纹条件
- 亮纹出现在两条缝的光程差为整数个波长处。
- 条件是 $d\sin\theta = m\lambda$,其中 $m = 0, 1, 2, \ldots$
- 更近的缝(更小的 $d$)或更长的波长使条纹分得更开。
- 测量条纹间距就能算出光的波长。
A bright fringe forms where the path difference from the two slits is: · 当来自两个狭缝的路径差为以下哪种情况时，形成亮纹：
Bright fringes need $d\sin\theta = m\lambda$ — a whole number of wavelengths. · 亮条纹需要$d\sin\theta = m\lambda$——整数倍的波长。
If the slit separation $d$ is halved, the fringe spacing: · 如果狭缝间距$d$减半，条纹间距将：
Fringe spacing goes as $1/d$, so halving $d$ doubles the spacing. · 条纹间距正比于$1/d$，因此减半$d$会使间距加倍。
A dark fringe forms where waves from the two slits arrive out of phase and cancel. · 当来自两个狭缝的波到达时反相并相互抵消，形成暗纹。
Out-of-phase arrival gives destructive interference — a dark fringe. · 反相到达导致相消干涉——形成暗纹。
Diffraction gratings
- A diffraction grating 衍射光栅 has thousands of fine slits packed together.
- It splits light into very sharp, bright spots — far cleaner than two slits.
- It also spreads different colours by different angles, making a spectrum.
- Gratings are used in spectrometers to identify the elements in stars and samples.
衍射光栅
- 衍射光栅有上千条紧密排列的细缝。
- 它把光分成非常尖锐、明亮的光点——比两条缝干净得多。
- 它还把不同颜色分到不同角度,形成光谱。
- 光栅被用在光谱仪中,识别恒星和样品中的元素。
A device with thousands of fine slits that splits light into sharp spots is a diffraction . · 一种拥有数千个精细狭缝、能将光分解为锐利光点的装置称为衍射。
A diffraction grating gives very sharp, bright maxima. · 衍射光栅能产生非常锐利、明亮的极大值。
Select all · 所有 true statements about the double slit and gratings. · 选择关于双缝和光栅的所有正确陈述。
Bright = whole-wavelength path difference; interference proves light is a wave; gratings make spectra. The pattern is interference, not independent torches. · 亮纹对应整数波长路径差；干涉证明光是波；光栅产生光谱。该图样是干涉，而非独立光源。
The double-slit fringes come from interference, not from the slits acting as tiny torches — that's why you get a pattern of stripes, not two bright bars. Bright fringes need a path difference of a whole number of wavelengths ($d\sin\theta = m\lambda$); half-wavelengths give dark fringes.
双缝条纹来自干涉,而非缝像小手电筒那样发光——这就是为什么你得到条纹图样,而非两条亮带。亮纹需要整数个波长的光程差($d\sin\theta = m\lambda$);半波长给出暗纹。
In a double-slit setup, the slit separation is halved. What happens to the fringe spacing?
- Fringe spacing goes as $1/d$, so halving $d$ doubles the spacing.
- The bright stripes move further apart on the screen.
在双缝装置中,缝间距减半。条纹间距会怎样?
- 条纹间距按 $1/d$ 变化,所以 $d$ 减半使间距加倍。
- 亮纹在屏幕上分得更开。
Young's double slit makes bright and dark fringes by interference — bright where $d\sin\theta = m\lambda$ (whole-number path difference). Closer slits or longer wavelengths spread the fringes wider. A diffraction grating (thousands of slits) gives sharp spots and splits light into a spectrum.
杨氏双缝通过干涉造出明暗条纹——$d\sin\theta = m\lambda$(整数光程差)处为亮。更近的缝或更长的波长使条纹更宽。衍射光栅(上千条缝)给出尖锐光点并把光分成光谱。