27.32. Part2_2¶
电磁波谱：光子
电磁现象的基本单位是 光子 （量子物理学中的一种量子形式）。这种亚原子粒子包括物质被热激发时所发出的辐射，或由核过程（聚变、裂变）或用其他辐射轰击所发出的辐射。光子是无质量的，以30万公里/秒（186000英里/秒）的光速运动。令人惊讶的是，这些粒子也以波的形式运动，因此具有“双重”性质。这些波遵循我们用正弦（三角）函数描述的模式，如下图中的二维所示。
波上两个相邻峰之间的距离就是它的波长。在一秒钟内通过一个参考的峰的总数就是波的频率（以每秒周期和赫兹为单位）。我们说一个光子能量，我们用普朗克的一般方程来确定：
在哪里？ v 有一些离散值由（ v 2 - v 1 ）换言之，特定的能量变化的特征是以特定频率产生发射的辐射（光子）。 v 以及相应的波长 l .
I-4 ** ** 上面的方程有什么问题吗？ ** ** 回答**
波长是频率的倒数（较高的频率与较短的波长有关；较低的频率与较长的频率有关），如关系式所示：
在哪里？ c is 表示光速的常数，这样我们也可以把普朗克方程写成
I-5 State a very simple mnemonic phrase (one that helps your memory) for associating the energy level (amount of energy) with wavelength. `ANSWER <answer.html#I-5>`__
I-6: Calculate the wavelength of a quantum of radiation whose photon energy is 2.10 x 10:sup:`-19` Joules; use 3 x 10:sup:`8` m/sec as the speed of light c. `ANSWER <answer.html#I-6>`__
I-7 ： ** ** 无线电台以120兆赫（兆赫或一百万周期/秒）的频率广播；相应的频率是多少米（提示：将兆赫转换成赫兹单位）。 ** ** `答案
The number 10:sup:-34` (incredibly small) or 1012 trillion (very large) is a shorthand notation that allows one to express very large and very small numbers without writing all of the digits. It allows one to "normalize" a number by expressing it in two parts: the first part expresses the value of the number as a real value between .9999... and 10 exclusive; the second part of the number tells the number of places to shift the decimal point to the right or the left. One multiplies the first part of the number by the power of ten in the second part of the number to get its value. Consider the second part of the number, values assigned to the number 10n where n can be any positive or negative integer. A +n indicates the number of zeros that follow the number 10, thus for n = 3, the value of 103 is 1 followed by three zeros, or 1000 (this is the same as the cube of 10); 106 is 1000000, i.e., a 1 followed by six zeros to its right (Note: 100 = 1). Thus, 1060 represents 1,000,000,000,000,000... out to 60 such zeros. Likewise, 10-3 (where n = -3) is equal to 0.001, equivalent to the fraction 1/1000, in which there are two zeros (three places) before the decimal point at 1. ; 10-6 is evaluated as 0.000001. Any number can be represented as the product of its decimal expression (between .99999... and 10) and the appropriate power of 10, (10:sup:n). Thus, we restate 8345 as 8.345 x 103; the number 0.00469 is given as 4.69 x 10-3.`