Reflection and Refraction of Light at Plane and Spherical Surfaces

Introduction 

Light is one of the most important aspects of life, without which we won’t be able to see anything around us. It is one form of energy that enables us to watch the objects around us. In other words, it is one of the types of electromagnetic radiation that travels through medium or vacuum. There are two types of objects – luminous and non-luminous – around us. Luminous objects are known to possess their own light that enables us to watch them. Additionally, the objects that glow when current passes through them are also called luminous objects. 

Introduction to Light

It is a form of energy that enables us to watch the things present around us. When light travels from the source to the object, the light gets bounced back and enters the human eye. As the light travels to the eye, our brain starts interpreting the signal, because of which we can see the object. 

Nature of Light

The nature of light behaves as a ray (for example – reflection), as a wave (for example – diffraction and interference) and particle (for example – photoelectric). 

Reflection and refraction of light at plane and spherical surfaces

Explain the reflection and refraction of light when it strikes plane and spherical surfaces. 

Reflection Of Light At Plane and Spherical Surfaces 

Laws of Reflection

Reflection is based on two laws that are termed laws of reflection. 

First Law Of Reflection

 The angle made between the normal and the incident ray is equal to the angle made between the normal and reflected ray. The angle of incidence is represented by ∠i, where “i” represents the incident ray. In contrast, ∠r is the angle of reflection. Both angles are equal to each other. 

Second Law Of Reflection 

The three rays – incident, normal and reflected – lie in the same plane. 

Reflection Of Light At Plane Surfaces

When the light strikes the plane surface and comes back in the same medium, the occurring phenomenon is the reflection of light. And the surface from which the light gets reflected is known as the reflecting surface. When such a phenomenon occurs, the light obeys the two laws of reflection (discussed earlier). 

When a beam of light strikes the smooth surface and gets reflected at the same angle, the surface is known as a regular or smooth surface. In this phenomenon of light, the angle of incidence is equal to the angle of reflection, and the three lines lie in the same plane. 

On the other hand, when a beam of light strikes an irregular or rough surface, the beam light gets reflected with different angles of reflection. This process or phenomenon is known as irregular reflection, and such a surface is known as an irregular reflecting surface. 

Reflection Of Light At Spherical Surfaces 

A mirror or surface that resembles the shape of a sphere is termed a spherical mirror or surface. In other words, a spherical mirror looks like it is a part that has been cut from a sphere. Spherical mirrors are of two types – Concave mirrors and Convex mirrors. 

Concave mirror – Also referred to as converging mirrors, this type of mirror is known to converge the rays that fall on it. When a light beam strikes at the concave mirror, the light rays converge at a single point. And this type of mirror curves inward. Such mirrors are used as vehicle mirrors as well as in street lights. 

Convex mirror – Unlike Convex mirror, this type of mirror has an outward curve. The images formed by the Convex mirror are erect, virtual and diminished. When the beam of light strikes the surface, the lines get reflected by either diverging or spreading out. For this reason, these mirrors are known as diverging mirrors. 

Refraction Of Light At Plane Surfaces and Spherical Surfaces 

Refraction of light is a surface phenomenon in which the light transfers from one medium to another and changes its direction. In such a phenomenon, when the beam of light changes its medium, the speed of the light also changes. A medium can be of two types – rarer (when the speed of the light increases) and denser (when the speed of light decreases). 

Laws Of Refraction 

There are two laws of refraction. 

1. All the three rays – incident, normal and refracted – lie in the same plane. 
2. The ratio of the sine angle of incidence to the sine angle of refraction is always constant for a given pair of mediums. This law is also known as snell’s law. 

Refraction Of Light At Plane Surfaces 

When a ray of light strikes the plane surface (for instance, a rectangular glass slab), it bends as soon as it enters the other medium. After refracting from its original path, the light ray travels straight and comes out of the glass slab. As soon as it comes out, the ray again refracts and bends. This phenomenon in which light-bending occurs is known as the refraction of light. 

Refraction Of Light At Spherical Surfaces 

When two spherical lenses come in contact with each other (face to face), it forms a spherical lens shape. Spherical lenses are of two types – Concave lenses and Convex lenses. When the ray of light passes through the Concave lens, it forms a virtual, erect and diminished image. 

Conclusion 

Both Convex and Concave mirrors are used in daily lives, and both of them act differently. The size of the image formed by the mirrors depends on the distance between the mirror and the object. Here we’ve explained all the facts and factors related to the reflection and refraction of light at plane and spherical surfaces.