英语听力文摘 English Digest 195、高强度气体放电灯-英语课

时间：2019-02-24 作者：英语课 分类：英语听力文摘 English Digest

英语课

　　Why Are Some Headlights Blue-High Intensity 1 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 wavelengths 2, 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 scatters 4 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 scatter 3 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.