📚 IGCSE AQA Science: Light | IGCSE AQA 科学：光 考点精讲
Light is a fundamental topic in IGCSE AQA Science, covering waves, optics, and the electromagnetic spectrum. Understanding how light behaves not only helps in explaining everyday phenomena but also forms the basis for technologies like lenses, optical fibres, and cameras. This revision guide summarises the key concepts, equations, and practical investigations you need to master.
光是 IGCSE AQA 科学中的一个基础主题，涵盖波动、光学和电磁波谱。理解光的行为不仅有助于解释日常现象，也是透镜、光纤和照相机等技术的基础。本考点精讲总结了你需要掌握的核心概念、公式和实验探究。
1. Nature of Light | 光的本质
Light is a transverse wave that does not require a medium to travel. It can travel through a vacuum at a speed of approximately 3.0 × 10⁸ m/s.
光是一种横波，不需要介质即可传播。它可以在真空中以大约 3.0 × 10⁸ m/s 的速度传播。
Light waves consist of oscillating electric and magnetic fields, which is why they are called electromagnetic waves.
光波由振荡的电场和磁场组成，因此它们被称为电磁波。
In IGCSE, we often use ray diagrams to represent the direction of light travel. A ray is a straight line with an arrow indicating direction.
在 IGCSE 中，我们常用光线图来表示光的传播方向。光线是带有箭头的直线，箭头指示方向。
2. Reflection | 反射定律
When light hits a smooth surface, it bounces back. This is called reflection. The law of reflection states that the angle of incidence (i) equals the angle of reflection (r), both measured from the normal.
当光照射到光滑表面时，会反弹回来，这称为反射。反射定律指出入射角（i）等于反射角（r），两者均从法线量起。
Angle of incidence i = Angle of reflection r
入射角 i = 反射角 r
The incident ray, reflected ray and normal all lie in the same plane.
入射光线、反射光线和法线都在同一平面内。
An image formed in a plane mirror is virtual, upright, laterally inverted and the same size as the object. The image distance behind the mirror equals the object distance in front.
平面镜所成的像是虚像、正立、左右颠倒，且与物体大小相等。像在镜后的距离等于物体在镜前的距离。
3. Refraction | 折射
Refraction is the bending of light as it passes from one transparent medium to another due to a change in speed.
折射是光从一种透明介质进入另一种介质时，因速度改变而发生弯曲的现象。
When light enters a denser medium (e.g. from air to glass), it slows down and bends towards the normal. When it enters a less dense medium, it speeds up and bends away from the normal.
当光进入光密介质（例如从空气到玻璃）时，速度减慢并向法线偏折。当进入光疏介质时，速度加快并偏离法线。
The refractive index n of a material is given by Snell’s law: n = sin i / sin r, where i is the angle in air (or vacuum) and r is the angle in the material.
材料的折射率 n 由斯涅尔定律给出：n = sin i / sin r，其中 i 是空气中的夹角，r 是材料中的夹角。
Refraction explains why objects appear displaced when viewed through water or glass.
折射解释了为什么透过水或玻璃观察物体时，物体看起来发生了移位。
4. Total Internal Reflection | 全内反射
Total internal reflection (TIR) occurs when light travelling in a denser medium hits a boundary with a less dense medium at an angle greater than the critical angle.
当光在光密介质中传播，并以大于临界角的角度入射到与光疏介质的边界时，会发生全内反射（TIR）。
The critical angle c is given by sin c = 1 / n.
临界角 c 满足公式：sin c = 1 / n。
For TIR to happen, two conditions must be met: the light must travel from denser to less dense medium, and the angle of incidence must be greater than the critical angle.
发生全内反射必须满足两个条件：光必须从光密介质射向光疏介质，且入射角必须大于临界角。
TIR is used in optical fibres to transmit light signals over long distances with very little loss.
全内反射被用于光纤中，以极低的损耗长距离传输光信号。
5. Dispersion and Colour | 色散与颜色
White light is a mixture of all colours of the visible spectrum. Dispersion is the splitting of white light into its constituent colours when it passes through a prism, due to different colours refracting by different amounts.
白光是可见光谱中所有颜色的混合。色散是指白光通过棱镜时被分解为其组成颜色的现象，这是因为不同颜色的光折射程度不同。
The order of colours from least to most refraction is: Red, Orange, Yellow, Green, Blue, Indigo, Violet (ROYGBIV). Red deviates least, violet deviates most.
颜色从折射最少到最多的顺序是：红、橙、黄、绿、蓝、靛、紫（ROYGBIV）。红色偏折最小，紫色偏折最大。
Filters absorb certain colours and transmit others. A red filter only transmits red light and absorbs others. Coloured objects reflect certain colours and absorb the rest; a blue object reflects blue light and absorbs others, appearing black in red light.
滤光片吸收某些颜色并透射其他颜色。红色滤光片只透射红光，吸收其他颜色。彩色物体反射特定颜色并吸收其余；蓝色物体反射蓝光而吸收其他，在红光下呈现黑色。
6. Lenses and Image Formation | 透镜与成像
There are two main types of lenses: converging (convex) and diverging (concave). A converging lens brings parallel rays to a focus at the principal focus. A diverging lens causes parallel rays to spread out, appearing to come from a principal focus on the same side.
主要有两种透镜：会聚透镜（凸透镜）和发散透镜（凹透镜）。会聚透镜使平行光线会聚于焦点。发散透镜使平行光线发散，看起来像是从同侧的焦点发出。
Key terms: focal length f is the distance from lens centre to principal focus. The lens formula is 1/f = 1/v + 1/u, where u is object distance, v is image distance. Magnification M = v/u = hᵢ/hₒ.
关键术语：焦距 f 是透镜中心到焦点的距离。透镜公式为 1/f = 1/v + 1/u，其中 u 为物距，v 为像距。放大率 M = v/u = hᵢ/hₒ。
Real images are formed when rays actually meet; they can be projected onto a screen. Virtual images are formed when rays appear to diverge from a point; they cannot be projected.
实像由光线实际会聚形成，可以投射到屏幕上。虚像是光线看起来从某点发出，不能投影。
For a convex lens: object beyond 2F gives real, inverted, diminished image; at 2F gives same size; between F and 2F gives enlarged, real, inverted; at F gives no image; between lens and F gives virtual, erect, magnified (magnifying glass).
对于凸透镜：物体在 2F 之外时，成倒立缩小的实像；在 2F 处等大；在 F 与 2F 之间成放大倒立实像；在 F 处不成像；在透镜与 F 之间成正立放大的虚像（放大镜）。
7. The Eye | 眼睛
The eye contains a convex lens that focuses light onto the retina, where images are formed. The ciliary muscles change the lens shape to focus on near or far objects (accommodation).
眼睛包含一个凸透镜，将光聚焦到视网膜上形成图像。睫状肌改变晶状体形状以对近处或远处物体进行聚焦（调节）。
Short-sightedness (myopia) occurs when the eye lens is too strong or eyeball too long, causing distant objects to focus in front of the retina. It is corrected with a diverging (concave) lens.
近视（myopia）是由于眼晶状体屈光力过强或眼球过长，使得远处物体成像在视网膜前方。可用发散透镜（凹透镜）矫正。
Long-sightedness (hyperopia) occurs when the lens is too weak or eyeball too short, causing near objects to focus behind the retina. It is corrected with a converging (convex) lens.
远视（hyperopia）是由于晶状体屈光力不足或眼球过短，使得近处物体成像在视网膜后方。可用会聚透镜（凸透镜）矫正。
8. Visible Light and Electromagnetic Spectrum | 可见光与电磁波谱
Visible light is a small part of the electromagnetic spectrum, which also includes radio waves, microwaves, infrared, ultraviolet, X-rays and gamma rays. All electromagnetic waves travel at the speed of light in a vacuum and are transverse.
可见光是电磁波谱的一小部分，电磁波谱还包括无线电波、微波、红外线、紫外线、X 射线和伽马射线。所有电磁波在真空中都以光速传播，且是横波。
The order of the spectrum by increasing wavelength: gamma, X-rays, UV, visible, infrared, microwaves, radio. The visible spectrum ranges from about 400 nm (violet) to 700 nm (red).
按波长递增顺序排列：伽马射线、X 射线、紫外线、可见光、红外线、微波、无线电波。可见光谱范围大约从 400 nm（紫色）到 700 nm（红色）。
Different parts of the spectrum have different uses and dangers, e.g. infrared for thermal imaging, ultraviolet for tanning but can cause skin cancer, X-rays for medical imaging.
光谱的不同部分有不同的用途和危害，例如红外线用于热成像，紫外线用于晒黑但可能导致皮肤癌，X 射线用于医学成像。
9. Practical Investigations | 实验探究
Reflection experiment: Using a ray box, plane mirror and protractor to measure angles i and r, verifying the law of reflection.
反射实验：使用光线盒、平面镜和量角器测量入射角和反射角，验证反射定律。
Refraction experiment: Aim a ray of light at a glass block, trace the incident and refracted rays, measure angles and calculate refractive index.
折射实验：将光线射向玻璃块，描绘入射和折射光线，测量角度并计算折射率。
Lens experiment: Use a convex lens and a screen to find the focal length by focusing a distant object, or investigate image formation for different object distances.
透镜实验：使用凸透镜和屏幕，通过聚焦远处物体来求焦距，或研究不同物距下的成像情况。
Safety: Avoid looking directly at bright light sources; handle glass blocks and lenses with care.
安全：避免直视强光源；小心操作玻璃块和透镜。
10. Key Equations and Calculations | 关键公式与计算
Master these four equations for the exam. They must be applied with correct units and rearrangements.
熟练掌握这四个公式，考试中需正确使用单位并进行变形。
The refractive index equation: n = sin i / sin r, where i is angle in air, r is angle in material.
折射率公式：n = sin i / sin r，i 为空气中角度，r 为介质中角度。
The critical angle equation: sin c = 1 / n.
临界角公式：sin c = 1 / n。
The lens formula: 1/f = 1/v + 1/u, with sign conventions (real is positive for convex lens).
透镜公式：1/f = 1/v + 1
Published by TutorHao | IGCSE Science Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
屏轩国际教育cambridge primary/secondary checkpoint, cat4, ukiset,ukcat,igcse,alevel,PAT,STEP,MAT, ibdp,ap,ssat,sat,sat2课程辅导，国外大学本科硕士研究生博士课程论文辅导Cancel reply