KS3 CIE Light Revision Questions | KS3 CIE 光学复习题

📚 KS3 CIE Light Revision Questions | KS3 CIE 光学复习题

This revision guide covers the main KS3 CIE light topic with concise explanations and exam-style quick questions. Work through each section, attempt the question, and then check the answer.

本复习指南涵盖 KS3 CIE 光学主题的主要知识点，配有简洁的解析和考试型快速问题。请逐节学习，先尝试回答问题，再核对答案。

1. How Light Travels and Shadows | 光的传播与影子

Light travels in straight lines called rays. We draw rays with arrows to show the direction of travel. A shadow forms when an opaque object blocks light, because light cannot bend around the object in normal conditions.

光沿直线传播，我们把带箭头的线称为光线，箭头表示传播方向。当不透明物体挡住光时就会形成影子，因为光在通常情况下不能绕到物体后面。

Quick question: Why is a shadow sharper when the light source is very small?

快速问题：为什么光源很小时影子边缘更清晰？

Answer: A small source behaves almost like a point source, so rays spread out less and the edge between light and dark is sharper than with a large extended source.

答案：小光源近似点光源，光线发散较少，明暗边界比大光源时更清晰。

Transparent materials let most light pass through, translucent materials scatter light, and opaque materials do not let light pass through.

透明材料让大部分光通过，半透明材料会散射光，不透明材料不让光通过。

2. The Law of Reflection | 光的反射定律

The law of reflection states that the angle of incidence equals the angle of reflection. Both angles are measured from the normal, which is an imaginary line drawn at 90° to the mirror surface.

反射定律指出入射角等于反射角。两个角都从法线量起，法线是画在与镜面成90°方向上的一条假想线。

The law can be written as i = r, where i is the angle of incidence and r is the angle of reflection.

该定律可写为 i = r，其中 i 是入射角，r 是反射角。

Quick question: A ray hits a plane mirror at 30° to the mirror surface. What is the angle of incidence?

快速问题：一条光线以与镜面成30°角射向平面镜，入射角是多少？

Answer

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