反射和反射定律

反思是我们在日常生活中遇到的一个非常基本的过程。我们无法想象没有反思的生活。我们能够看到的东西是由于光线通过物体落在我们的眼睛上并且我们能够看到的反射。我们能够在镜子或河流中看到自己的脸，背后的原因是反射。反射也负责我们听到的声音的回声，这是由于声音的反射。反射也用于寻找海洋的深度。

从上面的段落可以看出，反射是我们生活中非常普遍的现象，研究这种自然现象对于更好地了解这个宇宙很重要。

Optics is a branch of physics that deals with the phenomenon related to light. It is further divided into two sub-branches: 

• Ray optics: Ray optics is based on rectilinear propagation of light, and deals with mirrors, lenses, reflection, refraction, etc. Ray optics deals with the phenomenon in which light is being treated as a ray mean it cannot bend while travelling.
• Wave optics: Wave optics is a branch in which a wave is associated with light, and it explains phenomena such as diffraction, interference, polarization etc.

射线光学处理光被视为波的现象，这意味着它可以在传播时弯曲。射线光学还有许多子主题，如反射、折射等。在本文中，我们将了解反射及其定律。

什么是光的反射？

Reflection is natural phenomenon of bouncing back of light rays when it falls on a smooth, shiny surface say mirror. This is what enables us to look at the world around us because light ray which is reflected from these surfaces falls on our retina and this allows us to see.

落在镜子上的光线称为入射光线，从镜子反射回来的光线称为反射光线。中间的虚线表示为法线，它始终垂直于镜子。法线、入射光线和反射光线在镜子上的同一点相遇。

反射

反射的类型

特定反射创建图像。当我们旋转它时，我们可以观察到图像是倒置的，就好像它是从平面反射的一样。曲面反射可以放大或缩小图像，因此曲面镜可能具有光焦度。例如，球面或抛物面镜通常具有球面或抛物面。在此基础上，反射分为两种：

• 规则反射：规则反射是一种通过光滑表面进行的反射。在这种类型的反射中，所有反射光线相互平行，所有入射光线也相互平行。它遵循反射定律。这种反射形成的印象非常明亮和清晰。

例如反射通过平面镜。

• 不规则反射：在这个宇宙中发生的大多数反射是来自粗糙和不规则表面的反射。这种类型的反射称为不规则反射或漫反射。在这种类型的反射中，只要入射光线平行，反射光线就不平行。这种反射形成的图像是扭曲的，难以识别。

例如通过墙壁反射。

不规则反射

反射定律

After learning the meaning of reflection, one need to grasp the two laws that govern it. These rules can be used to calculate the incident ray’s reflection on various surfaces such as a plane mirror, water, metal surfaces, and so on. Consider the following laws of reflection in the case of a plane mirror:

Laws of Reflection

• When the light rays falls on the smooth surface, the angle of reflection is equal to the angle of incidence.

For the given case, ∠AOB is the angle of incidence (∠i) and ∠COB is the angle of reflection (∠r) then, according to the first law of reflection, this can be written as:

∠AOB = ∠COB

or 

∠i = ∠r

• The incident ray, the normal and the reflected ray must lie in the same plane.

Hence, in this case, the incident ray AO, the reflected ray CO, and the normal BO to the surface, all lie in the same plane.

反射的应用

• 潜望镜中使用反射来观察潜艇。
• 反射是我们看到物体的原因，因为图像是在我们的视网膜上形成的，大脑通过信号对其进行操作。
• 如上所述，凹面镜和凸面镜的反射有许多用途。
• 反射特性用于医学领域的诊断和光通信。
• 利用声光的反射定律，我们可以准确地测量到物体的距离。
• 反射是我们听到声音回声的原因。

日常生活中光反射的例子

以下是日常生活中光反射的一些最迷人的例子：

• 天空的蓝色：因为光线照射到大气中的不同粒子时会向各个方向散射，所以天空是蓝色的。因为蓝色的波长比红色短，所以散射更多。这就是为什么天空看起来是蓝色的。
• 日落的红色：日落是红色的，因为天空已经散射了从一天开始就在大气中传播的大部分蓝光。结果，在日落期间，红光占主导地位。
• 云看起来是白色的：因为云中的水滴明显大于光的波长，所以它们看起来是白色的。结果，所有颜色分散在不同的方向以产生白色。

示例问题

问题1：如果反射角为45°，求光线的入射角。

解决方案：

Since, ∠i = ∠r

Therefore, 

∠i = 45°

So, the angle of incidence of light ray is 45°.

问题2：如果镜子与入射光线的夹角为30°，求法向光线与反射光线的夹角。

解决方案：

As we know that mirror and normal are perpendicular to each other.

So, ∠i + angle between mirror and incident ray = 90°

∠i + 30° = 90°

∠i =60°

We know that,

∠i = ∠r

Therefore, 

∠i = 60° 

This implies,

∠r= 60°

So, the angle between normal and reflected ray is 60°.

问题 3：两个镜子彼此成 45° 角。一条光线以 30° 的入射角入射到第一反射镜上。求光通过第二个镜子的反射角。

解决方案：

For first mirror,

∠i = 30°

By law of reflection,

∠i  = ∠r

So, ∠r=30°

This reflected ray will act as an incident ray for other mirror. Let the angle of incidence on another mirror be i’ and angle of reflection be r’. A triangle will be formed at the corner with two sides as mirrors and third side as incident cum reflected ray.

First angle = 45°

Second angle = 90° – 30° = 60°

By angle sum property, 

Third angle = 180° – 45° – 60°= 75°

Now, we can easily find the angle of incidence of second mirror.

i’ = 90° – 75°= 15°

By law of reflection,

i’ = r’

So, r’ = 15°

Hence, the angle of reflection through second mirror is 15°.

问题4：如果镜子与入射光线的夹角为50°，求镜子与反射光线的夹角。

解决方案：

As we know that mirror and normal are perpendicular to each other.

So, ∠i + angle between mirror and incident ray = 90°

∠i + 50° = 90°

∠i =40°

We know that,

∠i = ∠r = 40°, 

So ∠r = 40°

As we know that mirror and normal are perpendicular to each other.

So, ∠r + angle between mirror and reflected ray = 90°

40° + angle between mirror and reflected ray = 90°

Angle between mirror and reflected ray = 50°

Hence, the angle between mirror and reflected ray is 50°.

问题5：如果两个镜子彼此平行，并且光线以35°角入射到其中一个镜子上，那么从另一个镜子反射后的反射角是多少。

解决方案：

Let the angle of incidence on first mirror be i and angle of reflection be r.

And Let the angle of incidence on another mirror be i’ and angle of reflection be r’ .

i=35°

By law of reflection, 

i = r

So, r = 35°

By simple mathematics, r and i’ form pair of alternate interior angles.

So, r = i’

i’ = 35°

Again, by law of reflection:

i’ = r’

So, r’=35°

Hence, the angle of reflection after reflecting from the other mirror will be 35°.