英语听力文摘 English Digest 195、高强度气体放电灯

　　Why Are Some Headlights Blue-High Intensity¹ Discharge Lamps
高强度气体放电（High-intensity discharge，简称HID）灯泡包含了下列这些种类的电灯：水银灯、金属卤化灯（也称作HQI）、高压钠灯、低压钠灯、高压水银灯，以及较少见的短弧氙气灯。这些灯泡种类的发光元件是一颗置于耐高温灯管（弧光管）内安定的电弧放电器，并有超过 3 W/cm2 (19.4 W/in.2) 的发光能力。
HID 灯通常应用在大面积区域且需要高品质的光线时，或针对能源效率、光源密度等特殊要求时。这些地方包括体育馆、大面积的公共区域、仓库、电影院、户外活动区域、道路、停车场或巷道。最近 HID 灯如金属卤化灯，常被用于零售店和住宅环境。HID 灯更实现到室内栽培上，特别是一些需要高品质强光的植物，如蔬菜和花卉。它们也可用于室内水族馆，重建近似于热带地区的强光。

　　有些 HID 灯像是水银灯会发出大量的紫外线，因此需要扩散器（diffusers）来阻挡紫外线的辐射。近几年来经常发生几个案件，因为瑕疵的扩散器，造成人们受到严重晒伤和电弧眼。现在均以规格来监控灯泡品质，否则灯泡会因为外层灯管破裂就马上烧掉。
最近 HID 灯常被使用于汽机车的头灯。这项应用在汽机车业界仍有各种不同的意见，主要在于 HID 灯有时会导致让人刺眼的强光。业界通常使用自动转向头灯（Automatic Self-leveling System）来降低这个问题，但这类的配备在大多车种都是昂贵的选配规格。然而，许多业者偏好使用这类光线，因为他们比一般头灯能发出较清澈、较明亮、较自然的光线。
Have you ever been driving along a country road at night, and all of a sudden a car comes around the bend and shines their high beams right into your eyes? Ugh, they’re so bright!
High Intensity Discharge Lamps
You also notice that their lights look a bit bluer than you’re used to. That’s because they might be. Regular headlights are made up of white light, which is a combination of all colors of the rainbow.
But these blue lights, while still containing a mixture of all colors, contain more blue wavelengths², making them appear more blue to our eyes.
Many luxury cars have these types of lights, called High Intensity Discharge lamps, because the headlights seem brighter under most conditions.
What Happens In Fog?
They actually make visibility worse.
Fog is made up of suspended water particles in the air, like a cloud settled down on the earth. But blue light scatters⁴ more effectively off these water particles than regular headlights do.
This is because the shorter the wavelengths of light, the better it scatters off of air and water particles.
Blue Light
So blue light, which has very short wavelengths, is much more likely to scatter³ than the longer wavelengths, like red light.
This means that when blue light hits the water particles, it’s more likely bounce off, going back into your eyes, and reducing your ability to see through the fog.
It also increases the glare for everyone, since blue light scatters better inside our eyes as well. In the regular headlights, there are still a fair amount of smaller wavelengths, so it scatters too. But since it also has more of the longer wavelengths, more light gets through the fog. So you can still see–sort of.

1 intensity   

n.强烈，剧烈；强度；烈度

参考例句：

• I didn't realize the intensity of people's feelings on this issue.我没有意识到这一问题能引起群情激奋。
• The strike is growing in intensity.罢工日益加剧。

2 wavelengths   

n.波长( wavelength的名词复数 )；具有相同的/不同的思路；合拍；不合拍

参考例句：

• I find him difficult to talk to—we're on completely different wavelengths. 我没法和他谈话，因为我们俩完全不对路。 来自《简明英汉词典》
• Sunlight consists of different wavelengths of radiation. 阳光由几种不同波长的射线组成。 来自辞典例句

3 scatter   

vt.撒，驱散，散开；散布/播；vi.分散，消散

参考例句：

• You pile everything up and scatter things around.你把东西乱堆乱放。
• Small villages scatter at the foot of the mountain.村庄零零落落地散布在山脚下。

4 scatters   

v.（使）散开， （使）分散，驱散( scatter的第三人称单数 )；撒

参考例句：

• He scatters money about as if he were rich. 他四处挥霍，好像很有钱。 来自《简明英汉词典》
• Truth raises against itself the storm that scatters its seeds broadcast. 真理引起了反对它自己的狂风骤雨，那场风雨吹散了真理的广播的种子。 来自辞典例句