# Refractive Index

Topics: Refraction, Total internal reflection, Snell's law Pages: 12 (1672 words) Published: December 29, 2013
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CONTENTS

Sl. No
Item
Page No.

1.
Objective

2.
Introduction

3.
Apparatus

4.
Theory

5.
Procedure

6.
Observations

7.
Diagrams

8.
Calculations + Graphs

9.
Precautions

10.
Bibliography

OBJECTIVES:

   To study the variation of the angle of deviation with the angle of incidence using Hollow Glass Prism and to determine the angle of minimum deviation.

   To find out the refractive index of various liquids using a Hollow Prism.

INTRODUCTION:

This project is of Investigatory Type.  In this project, a hollow prism has been used to calculate the refractive index of various liquids.  The hollow prism is filled with liquid and then the experiment is performed.

APPARATUS:

     Drawing Board
     Sheet of Paper
     Hollow Glass Prism
    Graph Paper
    Protractor
    Drawing Pins
   All Pins
    Pencil

THEORY:

Refraction:

In a homogenous medium, light travels along a straight line, but whenever it falls on a surface of another medium, a very small fraction of it is reflected back and most of the light passes into the medium, though with a change of direction.  This phenomenon of the bending of light at the surface of separation of the two medium is called refraction of light.

Causes of refraction:

This phenomenon of refraction takes place when a beam of light enters a medium in which light enters a medium in which light travels with a different velocity.

Laws Of Refraction:

1.       The incident ray, the refracted and the normal to the surface at the point of incidence lie on the same plane. 2.       For any two given media, the ratio of the sine of the angle of incidence to the angle of refraction is a constant, where it is the angle of incidence and is the angle of refraction.

Medium: The surrounding substance through which the light travels.           For a monochromatic light, the ratio of the sine of the angle of incidence to the sine of angle of refraction is a constant for any two given media.  If `I’ is the angle of incidence, and `r’ is the angle of refraction, then;                         Sine (I)

-------               =          Constant                         Sine(R)

The constant is called the refractive index.  For most purposes it may be assumed that the refractive index is with respect to air.

When light travels from a rarer to a denser medium, it bends towards the normal and vice versa when it goes from a denser to a rarer medium. It has been experimentally shown that

Velocity of light in air Refractive index of substance =      ------------------------------------                                                             Velocity of light in substance

Refraction through Prism:

A transparent medium bounded by two plane surface inclined to each other at an angle is called a Prism.  The angle between the two faces is known as the angle of the prism. Angle of deviation:  The angle through which the incident ray of light is deviated is called the angle of deviation.  In fact it is the angle between the emergent ray and the incident ray produced.

Angle of minimum deviation:  As the value of the angle of incidence (1) increases, the angle of deviation decreases till for a particular value of the angle of incidence, it attains a minimum value m, is called the angle of minimum deviation.

Critical angle :

It is that angle of incidence in the denser medium for which corresponding angle of refraction in the rarer medium is 90 degree.

I                               ...