Reflection of Light

Reflection of Light

Reflection is one of the distinctive properties of light. It is the reflection of light, which enables us to see anything. Light reflection occurs when a ray of light meets a smooth polished surface and reflects back. The incident light ray is said to be reflected off the surface when it lands on it. The beam that rebounds is known as the reflected ray. back. Normal is the name given to a perpendicular drawn on a reflective surface. The reflection of an incident beam on a plane mirror is seen in the diagram below.

Reflection: The rebound of rays of light from an elegant and glossy surface is called reflection or reflection of light. It is related to a football bouncing back after colliding with a wall or any hard surface.

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What is a Mirror, Exactly?

When you look in the mirror, you see a wonderful, clear image of yourself. It's not like your reflection in a gleaming automobile. And the vast majority of surfaces encountered in daily life aren't at all reflecting. At the kitchen table, you don't see your reflection at all. That's because, while the table appears to be smooth, it isn't. Most surfaces would reveal a panorama of peaks and valleys if examined under a microscope.

Various Types of Mirrors

The following are the most commonly used mirror types:

• Plane mirror

In the images formed by a plane mirror, the reflected images are reversed from left to right in their normal proportions. These are the mirrors that are utilised the most.

• Convex mirror

These are spherical mirrors bent outwards that provide a virtual, reduced, and erect image of a real thing.

• Concave mirrors

These are inwardly curved spherical mirrors, and the picture they produce is depending on the position of the object.

Spherical Mirrors vs Plane Mirrors

• A flat surface is referred to as a plane. A plane mirror is just a mirror with a fully flat, smooth surface. This prevents the image from becoming distorted. A fun-house mirror, on the other hand, maybe the polar opposite, with its different bends and curves making the image look silly.

• A sphere is a 3D replica of a perfect circle, with a constant radius and a consistent curve all the way around. So a spherical mirror is a sphere-shaped mirror with a continuous curve and constant radius of curvature.

• Spherical mirrors can be convex or concave depending on which side the mirrored surface is placed on. A convex mirror is a spherical mirror that has its reflecting surface on the outside of the spherical curve. On the other hand, a concave mirror is a spherical mirror with a mirrored surface on the inside of the curve.

• Virtual, upright representations the same size as the object are created by plane mirrors. By the way, virtual simply implies that the picture is produced behind the mirror rather than in front of it.

Laws of Reflection of Light

• The angle of reflection and incidence are equal.

• The incident ray, reflected ray and normal  point of reflection lies in the same plane.

The angle of incidence is denoted by 'i' and angle of reflection is denoted by 'r'.  The rule of reflection is valid to all types of reflecting surface.

Mirror and Reflection of Light

The mirror is a shiny polished object (glass) which reflects most of the rays of light falling upon it. One side of the mirror is cleaned with an appropriate material to make the opposite side reflective.

Types of Image Formed by Mirrors

• Real Image: Picture which is framed before the mirror and it very well may be acquired on a screen is called a genuine picture.

• Virtual Image: Picture which is framed before the mirror and it very well may be acquired on a screen is called a genuine picture.

Types of Mirror:

Plain Mirror: A mirror having a level surface is known as a plane mirror.

Formation of an image in the plane mirror:

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• A plane mirror dependably frames a virtual and erect picture.

• The separation of the picture and that of an item is equivalent from the mirror.

• The picture shaped by a plane mirror is horizontally modified.

Spherical Mirror

Mirrors having a curved reflecting surface are called round mirrors. A plane mirror constantly outlines a virtual and erect picture. 

• The partition of the image and that of a thing is equal from the mirror.

• The picture formed by a plane mirror is evenly adjusted. A round mirror is a piece of a circle.

Kinds of Spherical Mirror

• Concave Mirror: Spherical mirror with a reflecting surface bent inwards is known as a concave mirror.

• Convex Mirror: Spherical mirror with a reflecting surface bent outwards is known as a convex mirror.

Important terms in the case of a spherical mirror

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• Pole: The focal point of reflecting surface of a round mirror is known as Pole. Pole lies on the outside of the round mirror. It is commonly known by 'P'. 

• Centre of Curvature: The focal point of a circle; of which the reflecting surface of a round mirror is a section; is known as the center of curvature of the spherical mirror. Centre of curvature is not an element of a spherical mirror. Centre of curvature is  indicated  by the letter ‘C’.

On account of the concave mirror the center of curvature lies before the reflecting surface. Then again, the center of curvature lies behind the reflecting surface on account of a convex mirror.

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• The Radius of Curvature: The radius of the circle; of which the reflecting surface of a circular mirror is a section; is known as the Radius of Curvature of the round mirror. The range of curvature of a spherical mirror is signified by letter ‘R’.  Like the center of curvature, the radius of shape lies before the concave mirror and lies behind the convex mirror and isn't a piece of the mirror as it lies outside the mirror.

• Aperture: The diameter across from the reflecting surface of a round mirror is called aperture.

• Principal Axis: Imaginary line going through the center of curvature and pole of a round mirror are known as the Principal Axis.

• Focus or Principal Focus:  The point on a principal axis which parallel rays; originating from infinity; meet after reflection is known as the Focus or Principal Focus of the round mirror. It is signified by letter “F” 

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In a concave mirror, similar rays; coming from infinity; converge after reflection at the front of the mirror. Thus, the center point lies in front of a concave mirror.

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In a convex mirror, equivalent rays; coming from infinity; emerge to be diverging from the rear mirror. Thus, the focal point  lies at the rear of the convex mirror.

Focal length: The space from pole to focus is called focal length. Focal length is indicated  by the letter ‘f'. Focal length is equivalent to half of the radius of curvature.

Mathematically, we write:

\[ f = \frac{R}{2} \]

or

\[R = 2f \]

Reflection From a Spherical Mirror:

A spherical mirror is a type of mirror in which the reflecting surface is one of the parts of a hollow sphere of glass. Spherical mirrors are further subdivided into two types: 

1. Concave mirror: In a concave mirror the reflection of light is noticed at the bent surface or in other words at the concave surface. We can consider the inner polished surface of the regular spoon as an example for a concave spherical mirror. 

2. Convex mirror: In a convex mirror the reflection of light is observed at the bulging-out surface or in simple terms at the convex surface. The outer polished surface of a regular spoon can be considered as an example for convex mirrors.

Reflection of Rays parallel to Principal Axis

In the case of a concave mirror: A Ray equivalent to the principal axis passes during the principal focus after reflection from a concave mirror.

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In the same way, all equivalent rays to the principal axis pass through the principal focus after reflection from a concave mirror. Because a concave mirror converges the similar rays after reflection, thus a concave mirror is also known as a converging mirror.

In the Case of a Convex mirror: A  ray parallel to the principal axis appears to move away from the principal focus after reflecting from the surface of a convex mirror

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Likewise, all rays similar to the principal axis of a convex mirror appear to move away or come from principal focus after reflection from a convex mirror. Since a convex mirror diverges the similar rays after reflection, thus it is also known as a diverging mirror. 

Reflection of a Ray Passing Through the Principal Focus

In the Case of the Concave Mirror: Ray going through the principal focus goes parallel to the principal axis after the appearance on account of the concave mirror. 

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In the Case of the Convex Mirror: A ray guided towards principal focus goes parallel to the principal axis after reflecting from the outside of a convex mirror.

Ray passing through the Centre of Curvature:

In the Case of the Concave Mirror: Beam going through the center of curvature returns at a similar way subsequent to reflecting from the outside of an inward mirror.

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In the Case of the Convex Mirror: Beam seems to go through or coordinated towards the center of curvature parallel to the principal axis after reflecting from the surface of a convex mirror.

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Ray Incident Obliquely to the Principal Axis: Ray on a slope to the principal axis goes indirectly after reflecting from the pole of both concave and convex mirror and in the same direction.

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Image Formation by Concave Mirror

The arrangement of the image relies upon the place of the object. In the case of the concave mirror, there are six possibilities on which position of the object is placed.

a. Object at infinity

b. The object between infinity and the center of curvature (C)

c. An object at the center of curvature (C)

d. The object between the center of curvature (C) and Principal focus (F)

e. An object at Principal Focus (F)

f. Object among Principal Focus (F) and Pole (P)

An Object at Infinity

Since parallel rays coming from the object converge at the principal focus, F of a concave mirror; after reflection. Hence, when the object is at infinity the image will form at F.

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Properties of the image

• Point sized

• Highly diminished

• Real and inverted

The Object Between Infinity and Centre of Curvature

When the object is positioned between infinity and center of curvature of a concave mirror the image is created between the center of curvature (C) and focus (F).

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Properties of the image

• Diminished compared to the object

• Real and inverted

An Object at the Centre of Curvature (C)

When the object is located at the center of curvature (C) of a concave mirror, a real and inverted image is created at a similar position.

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Properties of the image

• Same size as the object

• Real and inverted

Object Among Centre of Curvature (C) and Principal Focus (F)

When the object is to be found between the center of curvature and the principal focus of a concave mirror, a real image is created beyond the center of curvature (C). 

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Properties of the image

• Larger than object

• Real and inverted

An Object at Principal Focus (F):

When the point is located at the principal focus (F) of a concave mirror, a highly inflated image is created at infinity.

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Properties of the image:

• Highly enlarged

• Real and inverted

The Object Between Principal Focus (F) and Pole (P):

When the point is located between principal focus and pole of a concave mirror, an inflamed, virtual and erect image is created behind the mirror.

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Properties of the image:

• Enlarged

• Virtual and erect

Image Formation by Convex Mirror

Two possibilities only are possible of the position of the object in the case of a convex mirror, i.e. the object at infinity and object among infinity and pole of a convex mirror.

An Object at Infinity: When the object is at the infinity, a point-sized image is formed at principal focus behind the convex mirror. 

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Properties of image: Image is extremely diminished, virtual and erect.

The Object Between Infinity and Pole: When the object is among infinity and pole of a convex mirror, a diminished, virtual and erect image is created among pole and focus behind the mirror.

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Characteristics of Object: object is diminished, virtual and erect.