There are the types of objects:

Luminous Objects

These are objects with their own source of light. Some examples of Luminous objects are tube light and sunlight. It is important to note that luminous objects do not necessarily have natural light. A passing current flowing through the tube light is also a luminous object. 

Non-Luminous Objects

The objects without their own source of light are Non-Luminous objects. Some examples of Luminous objects are walls and furniture. 

Besides, the tendency of light can have an impact based on how it falls on the surface. There can be two phenomena for this:

1. Absorbed

When light falls on any surface, it may be absorbed. It takes place on a black surface. Thus, black is the emitter of light and a perfect absorber. 

2. Pass through

When lights fall on any surface, they may pass through that object. However, all light rays do not have to pass through the surface. Some substances allow the light to pass. They are referred to as transparent. An example of this substance is glass, as it helps transmit all the light rays.

 

When light falls on a surface, it can perform two things: striking and bouncing. Thus, the phenomenon of striking and bouncing back of the light is called reflection. The daily life example of reflection is when we look in the mirror. Our replica in the mirror is an example of reflection. Therefore, we can define the properties and characteristics of the best reflector:

• It has a shiny surface.
• It has a smooth surface. 
• It also has a polished surface. 

Important Terminologies in Reflection

• A ray of light strikes the surface. It is an Incident, Ray.
• A point where the ray of light strikes is called the Point of Incidence.
• The perpendicular that is available to the point of incidence is Normal Ray.
• The ray of light that bounces back on striking the surface is called Reflected Ray.
• The angle between the normal ray and the incident ray is the Angle of Incidence.
• The Angle of Reflection refers to the angle between the normal and the reflected ray.
• A plane where the normal ray, incident ray, and the reflected ray lie in the Plane of Reflection.

Laws Of Reflection

There are two laws of reflection.

• Reflected ray, incident day and the normal ray lies on the same plane or surface. 
• The angle of incidence and reflection have similar angles. It means both are the same. 

Sources of Light: The types

There are different sources of light depending on the size of objects. These are:

1. Point Sources are too small.
2. Finite Sources have height. 

Types of Mirror

There are two types of mirrors depending on the reflecting surface. These are:

1. Plane mirrors have a plane reflection area.
2. Spherical mirrors have curved reflection areas. There are two types of spherical mirrors. They are:

• Convex mirror: Mirrors that are bulged are Convex mirrors. The reflection takes place through the outer surface.
• Concave mirror: These mirrors have depression. The reflection takes place through the inner surface.

Types Of Images

When the reflected rays appear or meet at a point, the images appear. Based on this concept, there are two types of image formation. These are:

1. Real image formation takes place when the reflected rays meet at a point. Also, real images are inverted and obtainable on screen. 

2. Virtual image formation occurs when reflected rays don't meet but appear to meet at a point. Also, virtual images are erect and unobtainable on screen. 

When the point object is kept in front of the plane mirror, the image formed is:

• Virtual
• Laterally Inverted
• Same Size
• The distance between the image and the object is the same as the mirror.
• Erect

A ray of light can pass through water, air, glass and other objects. It is important to highlight that a ray of light follows a straight line when it moves in one medium. However, the path changes when a ray of light moves from one medium to another. Based on this concept, we have two types of medium:

• The rarer medium has more speed of light and less density. One example is air, which is rarer than water. 
• A denser medium has a lesser speed of light and more density. One example is water is denser than air.

When the path of a ray of light changes, travelling from one medium to another is called refraction, it causes changes in the speed of light. We can also refer to refraction as the bending of light rays moving from one medium to another. 

Significant Terminologies in Refraction

• The ray of light that strikes the surface is Incident Ray.
• A point where the incident ray of light strikes the surface is the Point of Incidence.
• The ray of light that changes its path while travelling from one medium to another is Refracted Ray.
• The perpendicular that is available to the point of incidence is Normal Ray.
• The Angle of Incidence refers to the angle between the normal and incident rays.
• The angle between the refracted ray and the normal ray of light is the Angle of Refraction.

Law of Refraction

The substance obeys two laws of refraction during refraction. These are:

• The refracted, normal, and incident rays lie on the same plane.
• For a particular pair of media, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is always constant. 

Denser to rarer medium refraction

When a ray of light passes from a denser to a rarer medium, there is a change in the phenomenon. So, the light gets deflected away from the normal. Here, we see that the angle of refraction is greater than the angle of incidence. This refraction is from a denser to a rarer medium.

Rarer to denser medium refraction

It will be normal when light passes to a denser medium from a rarer medium. Here, we see that the angle of refraction is less than the angle of incidence. This refraction takes place from a rarer to a denser medium.

Reversibility of path of light

We understand that the path of light is reversible. It means a ray of light while entering from one side. However, when the light enters from the opposite end, the ray of light will follow the same sequence. This brings us to two rays of emergence:

• An Emergent Ray is a ray that passes through a medium and returns to its original medium.
• The angle of Emergence is between an emergent ray and a normal ray.

Lateral Displacement

One exciting phenomenon while understanding the reversibility of light is lateral displacement. It refers to the perpendicular shift in the incident ray. It happens when a ray of light travels through one medium and returns to its original medium.

1. Define the principal focus of a concave mirror.

After reflecting from a concave mirror, light beams parallel to the principal axis converge at a certain location on the principal axis. 

The major focus of the concave mirror is this spot.

2. The radius of curvature of a spherical mirror is 20 cm. What is its focal length?

Curvature radius (R) = 20 cm

spherical mirror radius of curvature = 2 focal length (f)

2f = R

f= R/2 = 20 / 2 = 10 f= R/2 = 20 / 2 = 10 f= R/2 = 20

As a result, the spherical mirror's focal length is 10 cm.

3. Name the mirror that can give an erect and enlarged image of an object.

A concave mirror is a mirror that can magnify and erect an object's image.

4. Why do we prefer a convex mirror as a rear-view mirror in vehicles?

A convex mirror is preferred as a rear-view mirror in cars and vehicles as it delivers a broader field of view, which helps the driver see most of the traffic behind him. 

Convex mirrors always reflect the objects in front of them in an erect, imaginary, and shrunken form.

The students will retain a good knowledge grasping power once they go through the content provided in this article.