Prefixes in A-Level Physics | A-Level 物理中的单位前缀

📚 Prefixes in A-Level Physics | A-Level 物理中的单位前缀

In A-Level Physics, very large and very small quantities appear constantly – from the wavelength of visible light to the power output of a national grid. SI prefixes allow us to write these values compactly and convert safely between units.

在 A-Level 物理中，极大和极小的量随处可见——从可见光的波长到国家电网的输出功率。国际单位制前缀让我们能够紧凑地书写这些数值，并在单位之间安全换算。

1. What Are SI Prefixes? | 什么是国际单位制前缀

An SI prefix is a letter or symbol placed before a unit to multiply that unit by a fixed power of ten. For example, the prefix kilo (k) means 10³, so 1 km = 10³ m and 1 kW = 10³ W.

国际单位制前缀是放在单位前面的字母或符号，用来将该单位乘以固定的十的幂。例如，前缀 kilo (k) 表示 10³，因此 1 km = 10³ m，1 kW = 10³ W。

Prefixes do not change the physical quantity being measured; they only rescale the unit. This means 25 mm and 0.025 m are exactly the same length, written in different units.

前缀不会改变被测量的物理量，它们只是重新标度单位。这意味着 25 mm 与 0.025 m 是完全相同的长度，只是用不同单位书写。

2. Why Prefixes Matter in Physics | 为什么前缀在物理中很重要

Most A-Level physics problems involve very large or very small quantities, such as the charge on an electron or the frequency of a radio wave. Prefixes reduce the chance of copying errors and make comparisons much easier.

大多数 A-Level 物理问题都涉及极大或极小的量，例如电子的电荷或无线电波的频率。前缀能减少抄写错误，并使比较变得容易得多。

In the exam, you will be expected to quote standard values with the correct prefix and to convert between prefixes quickly. For example, visible light has a wavelength around 5 × 10⁻⁷ m, which is normally written as 500 nm.

在考试中，你应当能用正确的前缀引用标准数值，并快速在不同前缀之间换算。例如，可见光的波长约为 5 × 10⁻⁷ m，通常写作 500 nm。

3. The Core Prefix Table for CIE A-Level | CIE A-Level 核心前缀表

The table below lists the prefixes you must know for the CIE A-Level Physics syllabus. Learn the exact symbol, power of ten, and one familiar example for each.

下表列出了 CIE A-Level 物理大纲中你必须掌握的前缀。请记住每个前缀的准确符号、十的幂和一个熟悉的例子。