📚 Investigating the Effect of Surface on Thermal Radiation | 探究表面对热辐射的影响
Thermal radiation is a key method of heat transfer that does not require a medium and travels as infrared waves. In IGCSE Physics, understanding how different surfaces emit and absorb thermal radiation is crucial, and the core practical 6.17 explores this phenomenon by measuring infrared emission from a Leslie cube and absorption by surface-treated materials.
热辐射是不需要介质并以红外波形式传播的一种重要传热方式。在IGCSE物理中，理解不同表面如何发射和吸收热辐射至关重要，核心实验6.17通过测量莱斯利立方体的红外发射以及表面处理材料的吸收来探究这一现象。
1. Introduction to Thermal Radiation | 热辐射简介
All objects with a temperature above absolute zero emit thermal radiation in the form of infrared waves. The rate of emission depends on the temperature and the nature of the surface. Hotter objects emit more radiation, but surface finish also plays a major role.
所有温度高于绝对零度的物体都会以红外波的形式发出热辐射。发射的速率取决于温度和表面性质。温度越高的物体辐射越强，但表面涂层也起着重要作用。
Infrared radiation is part of the electromagnetic spectrum with wavelengths longer than visible light. It can be detected by our skin as heat and measured using devices such as thermopiles or infrared thermometers.
红外辐射是电磁波谱的一部分，波长比可见光长。它可以被我们的皮肤感知为热量，并可使用热电堆或红外测温仪等设备进行测量。
2. Key Terminology: Emission and Absorption | 关键术语：辐射与吸收
Emission refers to the process by which a surface gives out thermal radiation. A good emitter is also a good absorber of radiation, according to the principle of reciprocity. Black, matte surfaces are excellent emitters and absorbers, whereas shiny, silvered surfaces are poor at both.
发射是指表面发出热辐射的过程。根据互易性原理，好的发射体同时也是好的吸收体。黑色哑光表面是优秀的发射体和吸收体，而光亮镀银表面在这两方面都很差。
Absorption refers to taking in thermal radiation. When infrared waves strike a surface, some energy is absorbed, warming the material. The rest may be reflected or transmitted. In this practical, we investigate both processes separately.
吸收是指吸收热辐射。当红外波照射到一个表面时，部分能量被吸收，使材料升温。其余的可能被反射或透射。在本实验中，我们将分别研究这两个过程。
3. Core Practical Overview | 核心实验概述
This practical consists of two parts: first, using a Leslie cube to compare the emission of infrared radiation from surfaces with different finishes; second, using metal plates or cans with different colours to compare the absorption of radiation from a heat source.
本实验包括两部分：第一部分使用莱斯利立方体比较不同涂层表面发射红外辐射的情况；第二部分使用不同颜色的金属板或罐子，比较它们对热源辐射的吸收情况。
The Leslie cube is a hollow metal cube with four vertical faces: one matte black, one shiny silver, one white, and sometimes one dull black or unpainted. Filled with hot water, each face emits radiation at the same temperature, allowing a fair comparison.
莱斯利立方体是一个中空金属立方体，有四个垂直面：一面哑光黑、一面光亮镀银、一面白色，有时还有一面暗黑或未涂漆。充满热水后，每个面在相同温度下发出辐射，可以进行公平比较。
4. Experiment 1: Investigating Emission Using a Leslie Cube | 实验一：使用莱斯利立方体研究发射
Apparatus: Leslie cube, kettle, hot water, infrared thermometer (or thermopile), ruler, stopwatch, heat-resistant mat.
仪器：莱斯利立方体、水壶、热水、红外测温仪（或热电堆）、直尺、秒表、隔热垫。
Method:
1. Fill the Leslie cube with freshly boiled water and seal the lid. Place it on a heat-resistant mat away from draughts.
1. 将刚烧开的水灌入莱斯利立方体并盖紧盖子。将其放置在隔热垫上，远离气流。
2. Using the infrared thermometer, measure and record the initial temperature of each face by positioning the detector 5 cm perpendicular to the surface. Ensure the same distance for all measurements.
2. 使用红外测温仪，将探测器垂直对准每个表面，距离5厘米，测量并记录各面的初始温度。确保所有测量距离相同。
3. Start the stopwatch and record the temperature of each face at regular intervals (e.g., every 30 seconds for 10 minutes).
3. 启动秒表，每隔一定时间（例如每30秒，持续10分钟）记录每个面的温度。
4. Take care to avoid touching the surfaces or allowing the sensor to move between readings. If using a thermopile, connect it to a millivoltmeter and record the reading which is proportional to radiation intensity.
4. 注意避免触碰表面或使传感器在读数之间移动。如果使用热电堆，将其连接到毫伏表，记录与辐射强度成正比的读数。
5. Repeat the measurements at least twice for reliability and average the results.
5. 至少重复测量两次以增加可靠性，并对结果取平均值。
5. Experiment 1: Results and Graph | 实验一：结果与图表
Typical results show that the matte black face gives the highest infrared reading, followed by white, then the shiny silver face. Over time, as the water cools, all readings drop, but the black surface maintains higher emission throughout.
典型结果显示，哑光黑面的红外读数最高，其次是白色面，最后是光亮银色面。随着时间推移，随着水温下降，所有读数都下降，但黑色面始终发射更强。
A graph of radiation reading (or temperature) versus time for each surface can be plotted. The slope of the cooling curve for the black surface is steeper initially, indicating higher rate of emission.
可以绘制每个表面的辐射读数（或温度）随时间变化的图表。黑色表面的冷却曲线初始斜率更陡，表明发射率更高。
It is important to note that the Leslie cube ensures all surfaces are at the same internal temperature, so differences in emission are purely due to surface nature.
重要的是，莱斯利立方体确保所有表面内部温度相同，因此发射差异完全由表面性质决定。
6. Experiment 2: Investigating Absorption Using Metal Plates | 实验二：使用金属板研究吸收
Apparatus: Published by TutorHao | IGCSE Science Revision Series | aleveler.com
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