Physical Optics- Physics - Lecture-1

Subject: Physics
Topic: Physical Optics
Subject Code: PHY4201
Lecture No: 1
Teacher Name: Md. Rezaul Karim

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Physical Optics

Content

	Introduction (Optics)
	Reflection
	Laws of Reflection
	Refraction
	Laws of Refraction
	Refractive Index
	Dispersion

Introduction

• Light is a electromagnetic radiation that can be detected by the human eyes.

• When light rays go straight into our eyes, we can see the object

Reflection of Light

Reflection:Whenlighttravellinginamediumencountersaboundaryleadingtoasecondmedium,partofthelightisreturnedtothefirstmediumfromwhichitcame.ThisphenomenoniscalledReflection

RegularReflection:Reflectionoflightfromsmoothsurfaceiscalledregularorspecularreflection

DiffuseReflection:Reflectionoflightfromroughsurfaceiscalleddiffusereflection

Laws of Reflection

First Law: The incident ray, the reflected ray and the normal of incidence are in the same plane.

Second Law: The angle of reflection is equal to the angle of incidence.

Refraction of Light

Refraction: When a ray of light travelling through a transparent medium encounters a boundary leading into another transparent medium, part of the ray enters the second medium, the phenomenon of changing the direction of the light ray is known as Refraction of light.

Angle of Refraction: The angle subtended by the normal and the refracted ray is the angle of refraction.

Laws of Refraction

First Law: The incident ray, the refracted ray and the normal at the point of incidence lie in the same plane.

Second Law: The ratio of the sine of the angle of incidence to the sine of the angle of refraction forany two given media is constant.(Snell’slaw)

Refractive Index

Refractive Index: It is defined as the ratio of velocity of light in a vacuum to the velocity of light in the medium      (μ=𝐶/ν)

•A medium with a relatively high refractive index is said to have a high optical density

•The refractive index depends not only on the substance but also on the wavelength of the light

Dispersion

Dispersion: When a ray of white light falls on a glass prism, it splits up into different colors.This display of colors is known as spectrum of the source of light. This separation of a composite beam into its constituent colors is called dispersion.