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Introduction of Wave Optics

Introduction of Wave Optics

Table of Contents

Introduction

Optics is the branch of physics which deals with the study of optical phenomena. Optics can be divided into two categories, which is Ray optics and Wave optics. Wave optics deals with the connection of waves and rays of light. It is used when the wave characteristics of light are taken in account. Wave Optics deals with the study of various phenomenal behaviors of light like reflection, refraction, interference, diffraction, polarization etc. It is otherwise known as Physical Optics.

For example, consider a compact disc. The colors which is reflected by the disc varies with different angle. This may be the evidence for wave character of light. It happens due to the interference of light waves which can be described by the concept of wave optics. It’s the same concept we see when we look at soap bubbles and a thin film of oil which is floating on surface of water. This reflection phenomena can be explained with the wave theory of light. Another example to explain this phenomenon is peacock and butterfly.

Evidence for the wave character of lightEvidence for the wave character of light

Wave optics explains why the sky is blue. The white light which is emitted by the sun is actually made up of all colors which are present in the beautiful rainbow. As per wave theory of light, light travels in wave forms too.Some light moves in long waves whereas,some other moves in the form of short waves.Here blue light waves are shorter than red light waves. All the light colors including blue light reaches the earth’s atmosphere and is scattered in all directions. As blue light is shorter and smaller wave,it is scattered more than any other colors in to the earth’s atmosphere.This is the reason for the blue colour of sky.

Wave forms of different colorsWave forms of different colors

History

Wave theory and Corpuscular theory

The wave theory of light was proposed by Christiaan Huygens.

Huygens mentioned that light is in a form of wave motion. Huygens stated that light is made up of waves that vibrates up and down and is perpendicular to the direction of light. He said that wavelength of the wave is very less when comparing with the dimensions of the object we measure. With the introduction of this concept, Huygens proved the laws of reflection and laws of refraction.

Huygens also found that the speed of light in denser medium is less compared to the speed of light in rarer medium. But this concept was not readily accepted and was in contradiction to the particle theory or the corpuscular theory of light proposed by Sir Isaac Newton. Issac Newton described that light is made up of tiny particles. Corpuscular theory states that the speed of light increases from rarer to denser medium. Hence in the beginning, wave theory of light was not accepted. Huygens proposed that light waves are longitudinal waves, but later it was found out that light waves are transverse in nature which means particles move perpendicular to the direction of wave.

Later, another scientist named Thomas Young performed the famous Interference experiment, which is called the Young’s double slit experiment (YDSE). This experiment proved the wave nature of light. After this, many other experiments were carried out which included the interference, diffraction and polarization patterns. These experiments were only explained by considering the wave nature of light. Finally wave theory came into existence. Corpuscular theory could not explain the various optical phenomena like interference, diffraction, polarization, dispersion and many others. However, both the corpuscular theory and wave theory could not explain the concept of photo electric effect of light.

Electromagnetic wave theory

James Clerk Maxwell proposed the electromagnetic wave theory of light propagation. We know that light is a form of electromagnetic wave, which means light waves are linked with changing electric and magnetic fields. Maxwell’s theory contributed to the inventions of Television, microwave, and many others. As all waves have common characteristics, light waves also have those properties like reflection, refraction, interference, diffraction, polarization etc. According to this theory, it is found out that light does not need any medium to travel. It can travel through empty space.

Electromagnetic wave theory

The Dual nature of light

Scientists later proved that light has dual nature. At times, it travels in the form of straight line. Sometimes light travels in the form of waves too.

Light behaves as both particle and wave

Light behaves as both particle and wave

Wave Characteristics

Light wave possesses a sinusoidal wave form. Wavelength and frequency are the two characteristics of light wave. Wavelength is defined as the distance between two peaks of waves. Frequency is the number of peaks that travels beyond a point in one second.

Summary

Optics, the branch which is the study of light phenomena is divided into two-ray optics and wave optics. Wave Optics deals with the study of various phenomenal behaviors of light like reflection, refraction, interference, diffraction, polarization etc. Huygens mentioned that light travels in the form of waves. In the beginning wave theory of light was not accepted due to Corpuscular theory proposed by Sir Isaac Newton. Newton stated that light consists of particles. Later by the emergence of Young’s experiment and various other experiments the wave theory came into existence. Maxwell mentioned that light is an electromagnetic wave. Later scientists found out that light travels both in the form of waves and particles.

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