📚 Visible Light and the Electromagnetic Spectrum | 可见光与电磁波谱
When you hear the number 680, you might think of a year, a distance, or a price. But in physics, 680 nm (nanometres) is the wavelength of red light — the longest wavelength that the human eye can see. This article explores the electromagnetic spectrum, focusing on visible light and the significance of 680 nm in IGCSE Science.
当你听到数字680，你可能会想到一个年份、一段距离或一个价格。但在物理学中，680纳米（nm）是红光的波长——人眼能看到的最长波长。本文将探讨电磁波谱，重点关注可见光以及680 nm在IGCSE科学中的重要意义。
1. What is the Electromagnetic Spectrum? | 什么是电磁波谱？
velength and frequency. All these waves travel at the same speed in a vacuum: 3 × 10⁸ m/s.
电磁波谱是所有电磁波的完整范围，按波长和频率排列。所有这些波在真空中的传播速度相同：3 × 10⁸ m/s。
The spectrum is continuous, but scientists divide it into seven main bands. From longest wavelength to shortest: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays.
频谱是连续的，但科学家将其分为七个主要波段。从最长波长到最短波长：无线电波、微波、红外线、可见光、紫外线、X射线和伽马射线。
All electromagnetic waves are transverse waves and can transfer energy. They do not need a medium to travel through, so they can travel through a vacuum.
所有电磁波都是横波，可以传递能量。它们不需要介质即可传播，因此可以在真空中传播。
Radio waves are used for radio and television broadcasting. Microwaves are used for satellite communication and heating food. Infrared is used in remote controls and thermal imaging. Visible light allows us to see. Ultraviolet is used for sterilisation. X-rays are used for medical imaging. Gamma rays are used in cancer treatment.
无线电波用于广播和电视发射。微波用于卫星通信和加热食物。红外线用于遥控器和热成像。可见光让我们看见。紫外线用于消毒。X射线用于医学成像。伽马射线用于癌症治疗。
2. The Visible Light Region | 可见光区域
Visible light is the only part of the electromagnetic spectrum that the human eye can detect. Its wavelengths range from about 400 nm (violet) to 700 nm (red).
可见光是电磁波谱中唯一人眼能检测到的部分。其波长范围约为400纳米（紫色）到700纳米（红色）。
In many textbooks, red is given as 700 nm, but deep red can be around 680 nm. The number 680 therefore lies in the red region, close to the boundary with infrared.
在许多教科书中
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