Reflection on A Plane Mirror

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What is Reflection of Light?

Light is a form of energy that brings forth the sensation of sight in our eyes. The path of light is always a straight line, and this single beam of light is called a ray of light. The process of sending back the light waves after falling on the surface of an object is called a reflection of light. The reflection of an object over a plane mirror forms images at many different places.

Light has two important properties, viz: reflection, and refraction.

The process by which light waves falling on a surface is sent by the surface is called reflection.  

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The objects having smooth, shiny, or polished surfaces reflect more light as compared to objects having unpolished or rough surfaces. 

The best reflector of light is silver. For this reason, a thin layer of silver metal is deposited on one side of the glass plate while making a plane mirror. This silver coating is protected by red color paint.

Types of Reflection

There are basically two types of reflection:

  • Specular/Regular reflection

  • Diffused/Irregular reflection

a. Specular/Regular Reflection

It is the mirror-like reflection of light rays. In this case, the light rays are reflected from a smooth, shiny, or polished surface like that of a mirror, and are reflected by a definite angle. 

Here, the incident ray & reflected ray makes the same angle with the normal. The formation of an image is due to regular reflection.

b. Diffused/Irregular Reflection

Diffused/Irregular reflection is a non-mirror type of reflection of light. In this reflection, the rays of light hit an irregular object with a rough surface and are reflected back from the object and scattered in all directions.

In this case, the incident ray and the reflected ray don't make the same angles with the normal. This is because the angle of incidence and the angle of reflection are different.

No image is formed by this type of reflection.

What are Laws of Reflection?

The laws of reflection of light can be applied both in the case of a plane mirror & the spherical mirror. Here, you can find detailed information regarding the images formed by the plane mirror.

First law of reflection: It states that the incident ray, reflected ray, and the normal (perpendicular to the surface of the object) at the point of incidence, lie in the same plane.

Second law of reflection: As per this law, the angle of reflection is always equal to the angle of incidence.

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Besides, one must bear in mind that when a ray of light normally falls (creating an angle of 90° with the surface) on the surface of a mirror, then both the angle of incidence and reflection will be zero. Moreover, this ray of light will be reflected back on the same path.

Plane Mirror Definition

A mirror with a flat or planar reflective surface is called a plane mirror. The reflected angle is always equal to the incident angle for all the light rays, which strike the plane mirror. 

The angle that occupies within the incident ray & the normal is called the angle of incidence. The normal is said to be an imaginary line that is perpendicular to the surface.

Reflection on a Plane Mirror

Here you will find a brief understanding of certain crucial terms, these are:

  • Incident Ray: The light ray that falls on the surface of a mirror is called the incident ray of light.

  • Point of Incidence: The incident ray that comes in touch with the surface of the mirror.

  • Reflected Ray: The light ray that is sent back by the mirror after striking the surface of the mirror is called the reflected ray.

  • Normal: It is an imaginary line perpendicular to the mirror's surface at the point of incidence.

  • Angle of Incidence: The angle made within the incident ray & the normal at the point of incidence is called the angle of incidence.

  • Angle of Reflection: The angle made within the reflected ray and the normal at the point of incidence is called the angle of reflection.

Images Formed by Plane Mirrors

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The nature of the image formed by a plane mirror is mentioned below:

● The image is virtual and erect.

● The size of the object equals to that of the size of the image.

● An image is formed behind the mirror.

● The distance between the image & the mirror is the same as the distance between the mirror and the object. 

● Image formed is laterally inverted.

The image is laterally inverted. This suggests, if you raise your left hand, it would appear that you have raised your right hand in the mirror.

Uses of Plane Mirror

  • Mirrors are used in the dressing table, bathrooms to see ourselves.

  • They are usually placed in the inside walls of jewelry shops to make it look big.

  • Mirrors are fitted at blind turns on the roads so that vehicles' drives can see vehicles coming from the other side.

  • Mirrors are used in making periscopes.

FAQ (Frequently Asked Questions)

Q1. Which among the Given List has Two Angles that are Equal to Each Other?

i. Reflection

ii. Refraction

iii. Diffraction

iv. None of the above

Ans- i. Reflection

As per the Snell's law of reflection, the angle of reflection is equal to the angle of incidence.

Q2. What are Some Characteristics of an Image Formed by a Plane Mirror?

  • The image is virtual and erect.

  • The image formed is laterally inverted.

  • Size of the image is equal to the size of the object.

  • The image and the object are equidistant from the mirror.

Q3. What are the Two Types of Mirrors?

Ans- There are two types of curved mirrors; they are a concave mirror and convex mirror. A curved mirror in which the center bulges out is called a convex mirror. The mirror in which the edges bulge out is called a concave mirror.

Q4. Where is the Focus of a Plane Mirror?

Ans- The focus of a plane mirror is located at infinity. As such, the focal length of the mirror is infinite.