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## 电子工程代写|光子简介代写Introduction to Photonics代考|The Electromagnetic Spectrum

The rainbow colors of visible light make up only a small portion of the electromagnetic spectrum. While the electromagnetic spectrum spans wavelengths from a fraction of a picometer to several hundred meters, the wavelengths of visible light extend only from about $400 \mathrm{~nm}$ for violet to about $700 \mathrm{~nm}$ for red. These wavelengths are not distinct boundaries; the wavelengths at which the visible spectrum fades away at either end depend somewhat on the individual as well as the viewing conditions. The colors of the visible spectrum, from long wavelength to short wavelength, can be remembered by the acronym “ROY G. BV”: red, orange, yellow, green, blue, violet.

Figure $2.5$ shows the electromagnetic spectrum with approximate wavelengths from wavelengths $10^{-14}$ meters to more than 1000 meters. Beginning at violet light and progressing toward shorter wavelengths we have ultraviolet (UV) rays, then $\mathrm{x}$-rays, and finally gamma rays. In the region beyond red are infrared (IR), microwaves, and radio waves. All of these terms describe electromagnetic radiation, differing only by wavelength.

What we call “light” usually means what humans are capable of sensing, that is, the visible spectrum. In some contexts, however, the word “light” includes portions of the UV and IR regions; this is sometimes called the optical spectrum. Human vision is limited to a small range of wavelengths because our retinal sensors cannot be stimulated by low-energy infrared light, and the lens of our eye blocks UV light. However, other animals, including many insects, can sense UV light, and photographs taken of flowers and butterflies illuminated with UV light often look very different from the same items illuminated with visible light. In fact, imaging with radiation from different parts of the spectrum allows scientists to study such diverse phenomena as crop diseases and star formation. Specialized film or detectors are used to create images over wavelengths of the electromagnetic spectrum invisible to human eyes. Chapter 12 will explore the science and technology of optical imaging.

## 电子工程代写|光子简介代写Introduction to Photonics代考|INTRODUCTION TO QUANTUM OPTICS

At the end of the 19th century, physicists were fairly certain that the science was complete in its description of the physical world and only minor details remained to be explained. One of these details was the photoelectric effect. The effect was puzzling because the emission of electrons from an illuminated metal depends upon the wavelength of the light, not the irradiance. For example, a certain metal target might emit electrons when illuminated with ultraviolet light but not when illuminated with red light, even if the red light strikes with a much higher irradiance than the UV.

The explanation of the photoelectric effect proposed by Einstein in 1905 is that the light striking the metal is a stream of particles, later given the name photons, and the energy of each photon is directly proportional to the frequency of the associated radiation. Mathematically
$$E=\mathrm{h} f .$$
The constant of proportionality, $\mathrm{h}$, is called Planck’s constant and is equal to $6.626 \times 10^{-34}$ joule ${ }^2$ second. The constant is named for Max Planck, sometimes called the “father of quantum physics,” who was the first to correctly describe the wavelength spectrum of radiation produced by a glowing hot object.

A photon can be described as the smallest division of a light beam that retains properties of the beam such as frequency, wavelength, and energy; it is a quantum unit of light energy. A photon is sometimes described as a wave packet that has specific energy content. Although we speak of photons as particles, they have some pretty bizarre properties. For example, a photon has energy, but no mass. It does carry momentum, and if it stops moving it ceases to exist!

## 电子工程代写|光子简介代写Introduction to Photonics代考| Introduction to QUANTUM OPTICS

$$E=\mathrm{h} f .$$

## MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。