Lenses and dispersion · 透镜与色散
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| dispersion/dɪˈspɜːʃn/ | 色散 | sè sàn |
| diverging lens/daɪˈvɜːdʒɪŋ lenz/ | 凹透镜 | āo tòu jìng |
| converging lens/kənˈvɜːdʒɪŋ lenz/ | 凸透镜 | tū tòu jìng |
| principal focus/ˈprɪnsɪpl ˈfəʊkəs/ | 焦点 | jiāo diǎn |
| focal length/ˈfəʊkl leŋθ/ | 焦距 | jiāo jù |
| real image/rɪəl ˈɪmɪdʒ/ | 实像 | shí xiàng |
| virtual image/ˈvɜːtʃuːəl ˈɪmɪdʒ/ | 虚像 | xū xiàng |
| spectrum/ˈspektrəm/ | 光谱 | guāng pǔ |
| monochromatic/ˌmɒnəʊkrəʊˈmætɪk/ | 单色 | dān sè |
Focusing and splitting light
- A magnifying glass makes tiny print big; a prism turns white light into a rainbow.
- Both use refraction — bending light in a careful, shaped way.
- Meet the lens and dispersion 色散.
聚焦和分裂光
- 一个放大镜把微小的字变大;一个棱镜把白光变成彩虹。
- 两者都用折射——以一种小心的、有形状的方式弯曲光。
- 认识透镜和色散。
Converging and diverging lenses 凹透镜
- A converging lens 凸透镜 is fat in the middle. It bends parallel rays inwards to meet at the principal focus 焦点.
- The distance from the lens to that focus is the focal length 焦距 $f$.
- A diverging lens is thin in the middle and spreads rays out.
A converging lens and its principal focus
会聚透镜与发散透镜
- 一个会聚透镜(converging lens)中间厚。它把平行光线向内弯曲以在主焦点(principal focus)相遇。
- 从透镜到那个焦点的距离是焦距(focal length)$f$。
- 一个发散透镜(diverging lens)中间薄并把光线散开。
一个会聚透镜和它的主焦点
Image formation by a converging lens · 会聚透镜的成像
Trace the three special rays from the object — where they meet is the image. Move the object closer than the focal point to flip it into a magnifying glass. · 从物体追踪三条特殊光线——它们相遇之处是像。把物体移到比焦点更近以把它翻转成一个放大镜。
A converging lens makes parallel rays of light: · 一个会聚透镜使平行的光线:
A converging (convex) lens bends parallel rays inward so they meet at the principal focus. · 一个会聚(凸)透镜把平行光线向内弯曲,使它们在主焦点相遇。
The distance from the lens to its principal focus is called the ____ length. · 从透镜到它的主焦点的距离被称为______距。
The focal length is the distance from the centre of the lens to the principal focus. · 焦距是从透镜中心到主焦点的距离。
Images from a lens
- A converging lens can make a real image 实像 — the rays really meet, so it can be shown on a screen (as in a camera or the eye).
- When the object is very close, it makes a larger virtual image 虚像 instead.
- Used close to the eye like this, the lens is a magnifying glass.
来自透镜的像
- 一个会聚透镜能产生一个实像(real image)——光线真的相遇,所以它能被显示在一个屏幕上(如在一个相机或眼睛中)。
- 当物体非常近时,它产生一个更大的虚像(virtual image)代替。
- 像这样靠近眼睛使用时,透镜是一个放大镜(magnifying glass)。
Used close to the eye as a magnifying glass, a converging lens makes a: · 像放大镜一样靠近眼睛使用时,一个会聚透镜产生一个:
With the object very close, the lens forms an enlarged, upright virtual image — a magnifying glass. · 物体非常近时,透镜形成一个放大的、正立的虚像——一个放大镜。
Dispersion
- A glass prism splits white light into a band of colours — the spectrum 光谱. This splitting is dispersion.
- The order is red, orange, yellow, green, blue, indigo, violet.
- Red bends least: it has the longest wavelength and lowest frequency. Violet is the opposite.
- Light of a single colour (one frequency) is monochromatic 单色.
色散
- 一个玻璃棱镜(prism)把白光分裂成一条彩色带——光谱(spectrum)。这个分裂是色散(dispersion)。
- 顺序是红、橙、黄、绿、蓝、靛、紫。
- 红弯曲最少:它有最长的波长和最低的频率。紫是相反的。
- 单一颜色(一个频率)的光是单色的(monochromatic)。
Put these spectrum colours in order of wavelength, longest first. · 把这些光谱颜色按波长,最长在先排序。
Red has the longest wavelength and violet the shortest, so: red, yellow, green, blue, violet. · 红有最长的波长而紫最短,所以:红、黄、绿、蓝、紫。
Which colour of visible light has the longest wavelength? · 哪种可见光颜色有最长的波长?
Red light has the longest wavelength and lowest frequency; violet has the shortest wavelength and highest frequency. · 红光有最长的波长和最低的频率;紫有最短的波长和最高的频率。
You've got it
- a converging lens brings parallel rays to the principal focus; lens-to-focus = focal length
- it makes a real image (on a screen) — or a magnified virtual image when the object is close (magnifying glass)
- a prism causes dispersion: white light → red…violet
- red = longest wavelength, lowest frequency; violet = shortest, highest
你掌握了
- 一个会聚透镜把平行光线带到主焦点;透镜到焦点 = 焦距
- 它产生一个实像(在屏幕上)——或当物体近时一个放大的虚像(放大镜)
- 一个棱镜造成色散:白光 → 红…紫
- 红 = 最长波长,最低频率;紫 = 最短,最高