Reflection of Light

What is reflection of light?

Have you ever wondered how we can see anything? When you enter a dark room, can you see things kept in the room? Of course not. But as soon as you turn on the light of the room, everything becomes visible.

What is happening here? When we turn on the light of the room, the rays of light fall on the objects, get reflected and received by our eyes causing us to see the objects around us.

The light, our eyes, and brain help us to see the beautiful world.

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In simple words, the bouncing back of light after hitting any surface is called a reflection of light. For example, we can see the moon because of reflection.

Types of reflection of light

Following are the three types of reflection:

  • Regular reflection/Specular reflection
  • Diffused reflection
  • Multiple reflections

Regular reflection/Specular reflection

When the beam of light falls on a polished or smooth surface, then it bounces back from the surface in the same direction. This phenomenon is called regular reflection of light or specular reflection.
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Characteristics of specular reflection:

  • Incident rays are parallel and uniform.
  • Reflected rays are parallel and uniform.
  • The reflected surface is polished or shiny.
  • Almost all the incident rays get reflected.
  • The angle of incidence and angle of reflection is the same.

Diffused Reflection

When the beam of light falls on a rough surface, then it reflects in different directions, which is called diffused reflection.
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Characteristics of diffused reflection:
  • Reflected rays are not parallel, they scatter in different directions.
  • The reflected surface is rough.
  • The angle of incidence and angle of reflection are different.

Multiple Reflection

A single image is formed when an object is placed in front of a mirror. What happens if we use two mirrors? We will see multiple images of one object or an image of an image.

This happens because the image formed by one mirror acts as the object for the second mirror. This phenomenon is called multiple reflections. The number of images depends on the angle between the mirrors.

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pic source: alamy.com

You might have seen this type of reflection while visiting the barbershop for your haircut. After the haircut, the barber holds a small mirror behind your head to show you the final cut. When this happens, apart from your head, you also see multiple images of yourself.

Terminology of reflection

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Incident ray: The ray of light falling on the surface of a mirror is known as an incident ray.

Point of incidence: The point where incident rays touch the surface of a mirror is called a point of incidence.

Reflected ray: The ray of light that bounces off from the mirror surface is called a reflected ray.

Normal: The perpendicular line drawn at the point of incidence to the surface of a mirror is called normal.

Angle of incidence: The angle between the incident ray and the normal at the point of incidence is called the angle of incidence.

Angle of reflection: The angle between the reflected ray and the normal at the point of incidence is called the angle of incidence.

Laws of Reflection

The laws of reflection determine the reflection of incident rays on the surfaces such as mirrors, smooth metal surfaces, and clear water. Here we are considering a plane mirror as shown in the figure below.

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Basically, there are two types of laws of reflection:

Law 1. The incident ray, the reflected ray, and the normal, all lie in the same plane.

Law 2. The angle of incidence is equal to the angle of reflection. ∠i = ∠r

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