# Reflection

Have you ever looked at yourself in a mirror or heard echoes in a tunnel? It's all possible because of something called reflection! In this article, we'll be talking specifically about the reflection of light. We'll start by defining what reflection is, and then we'll talk about the different types and causes of light reflection. We'll also take a look at the laws that apply to reflection. Towards the end, we'll provide some practical examples to help you better understand the concept of reflection. So, let's get started!

## The definition of reflection

In principle, light travels in a straight line as long as there is no event to stop it from doing so. A change of materials through which the light is travelling is such an event. Because light is a wave, it may be absorbed, transmitted, reflected, or a combination thereof. A reflection can take place at the boundary between two materials, also called media, and its definition can be stated as follows.

Reflection of light is the change in the direction of light once it hits the boundary between two media and travels back into the original medium. This boundary is called the reflection surface.

## Laws of reflection

To discuss the laws of reflection, we need a set-up (see the figure below). For a reflection, we need a reflection surface and an incoming ray of light, and we will automatically have a reflected ray of light that has a different direction than the incoming ray. The reflection surface has a perpendicular line through it called the normal, the incoming (or incident) ray makes an angle of incidence with the normal, and the reflected ray makes an angle of reflection with the normal. The laws of reflection are:

The incoming ray, the reflected ray, and the normal to the reflection surface are all in the same plane; The angle of incidence is the same as the angle of reflection:;The reflected ray is on the other side of the normal than the incoming ray.

Laws 1 and 3 are pretty intuitive and you may not need to remember them explicitly, but law 2 is important to remember. The laws are nicely illustrated in the figure below.

Here is a sample question about reflection. Q: Suppose we have a ray of light and it reflects off a reflection surface to produce a reflected ray of light. The incoming ray makes an angle of with the reflection surface. What is the angle of reflection? A: We have to read carefully here: the angle of incidence is the angle with the normal to the reflection surface, so the angle of incidence is. The laws of reflection now state that the angle of reflection is also.

Being able to draw rays of light that reflect off of surfaces is important. These drawings are called ray diagrams. The figure above is an example of a ray diagram.

## Types and causes of light reflection

There are two main types of light reflection, and their causes have to do with the reflection surface being smooth or rough.

### Specular reflection

Specular reflection is the reflection that is the result of the reflection surface being smooth.

A mirror and still water are good examples of smooth reflection surfaces. The smoothness of the reflection surface means that the normal to the reflection surface stays the same (in the case of flat reflection surfaces, or plane mirrors) or changes slowly and gradually (in the case of curved surfaces, which we will not go into further in this article) from place to place on the reflection surface. The laws of reflection now say that, because the normal is the same everywhere on the reflection surface, the reflected light from one ray of incoming light will all have the same direction.

This allows for virtual images, which are images of (real) objects that appear to be somewhere that they are not. The reason for this false appearance is that the light that reaches our eyes comes from a direction that is not the direction of the object. See the figure for an illustration. The information that the eye receives will tell it that the object at point A, say an apple, is somewhere behind the mirror (because our brains assume that the light has always travelled in a straight line), while in reality, the apple is in front of the mirror, next to the eye.

### Diffuse reflection

Diffuse reflection is the reflection that is the result of the reflection surface being rough.

Most regular things have a rough surface: bread, walls, trees, et cetera. The rough surface means that the normal to the reflection surface changes wildly between different places on the surface. The laws of reflection now say that, because the normal is so different, the direction of the reflected ray of light is also different from place to place: the reflected light gets diffused into different directions. See the figure below for an illustration of this effect. This also means that there is no such thing as a mirror image in the case of rough reflection surfaces.

## Examples of reflections

Seeing yourself in your bathroom mirror (which is a plane mirror that causes specular reflection) is an everyday example of a reflection of light. Another example of reflections is the diffuse reflection most objects produce, and how these determine what colour we perceive an object to be.

A green plant has a rough surface, so it reflects sunlight diffusely. However, some frequencies of the sunlight are absorbed more than other frequencies, making the reflected light waves have a different frequency spectrum than the incoming sunlight. It is the reflected light wave that hits our eyes, so their spectrum determines which colour we perceive the plant to be, which is green. Apparently, the non-green frequencies of light get absorbed more by the plant than the green frequencies do.

Reflection of light plays a crucial role in determining the colors of objects. For example, a red object reflects less of the red frequencies than it does of other frequencies. However, reflection isn't limited to light waves. Sound waves can also reflect off of surfaces like walls and caves, creating reverb and echoes. Sometimes, sound can appear to come from one side of a room when the source is on the other side, due to reflection. Bats use echolocation, which is the reflection of sound waves, to navigate their environment. Similarly, water waves can also be reflected when they hit a wall, with part of the wave being absorbed and the other part being reflected. These reflections follow the same laws we talked about earlier for light reflection.

## Importance of light reflection

Light reflection is incredibly important for life on Earth. Most objects do not emit visible light, so we can only see them because they reflect sunlight towards our eyes. Different materials reflect, transmit, and absorb different colors of light, which can provide animals with information about what an object is made of. There are two types of light reflection: specular reflection and diffuse reflection. Specular reflection happens off of smooth surfaces and creates virtual images, while diffuse reflection occurs off of rough surfaces, which is what most objects have. Reflection isn't just limited to light - other types of waves can also be reflected, like sound and water waves. This is what causes echoes and reverberation. Without reflection, we wouldn't be able to see much of the world around us.

## Reflection

What are types of reflection of light?

The two main types of reflection of light are specular and diffuse reflection. Specular reflection happens when the reflection surface is smooth, so the reflected light travels in one direction. Diffuse reflection happens when the reflection surface is rough. Still water and mirrors cause specular reflection, while most everyday objects cause diffuse reflection.

What is reflection?

Reflection of light is the change in the direction of light once it hits the boundary between two media and travels back into the original medium.

What is an example of reflection?

An example of reflection is light from the Sun that hits grass, of which a part is reflected towards your eye. This is how you see the grass.

What is the law of reflection?

The laws of reflection state that the angle of reflection is equal to the angle of incidence.

What is the importance of reflection of light?

The importance of reflection of light is that it enables animals to see. Most objects do not emit a lot of visible light themselves, so animals rely on the light from the Sun that reflects off objects towards their eyes to see those objects.

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