204529344 Hollow Prism Physics Investigatory Project Class 12 CBSE

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    INTRODUCTION

    In optics, a prism is a transparentoptical element with fat, polishedsuraces that reract light. Theexact angles between the suracesdepend on the application. The

    traditional geometrical shape isthat o a triangular prism with atriangular base and rectangularsides, and in colloquial use "prism"

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    usually reers to this type. Sometypes o optical prism are not in

    act in the shape o geometricprisms. Prisms can be made romany material that is transparent tothe waelengths or which they aredesigned. Typical materials include

    glass, plastic and fuorite. ! prismcan be used to brea light up intoits constituent spectral colors #thecolors o the rainbow$. Prisms canalso be used to refect light, or to

    split light into components withdi%erent polari&ations.

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    PRISM AND NATURE OF LIGHT

    'eore Isaac (ewton, it wasbelieed that white light wascolorless, and that the prism itsel

    produced the color. (ewton)sexperiments demonstrated that allthe colors already existed in the

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    light in a heterogeneous ashion,and that "corpuscles" #particles$ o

    light were anned out becauseparticles with di%erent colorstraeled with di%erent speedsthrough the prism. It was only laterthat *oung and +resnel combined

    (ewton)s particle theory withuygens) wae theory to show thatcolor is the isible maniestation olight)s waelength. (ewton arriedat his conclusion by passing the red

    color rom one prism through asecond prism and ound the colorunchanged. +rom this, heconcluded that the colors mustalready be present in the incoming

    light - thus, the prism did notcreate colors, but merely separatedcolors that are already there. ealso used a lens and a second

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    prism to recompose the spectrumbac into white light. This

    experiment has become a classicexample o the methodologyintroduced during the scienticreolution. The results o thisexperiment dramatically

    transormed the eld ometaphysics, leading to /ohn0oce)s primary s secondaryquality distinction. (ewtondiscussed prism dispersion in great

    detail in his boo 1ptics. 234 ealso introduced the use o morethan one prism to controldispersion.254 (ewton)s descriptiono his experiments on prism

    dispersion was qualitatie, and isquite readable. ! quantitatie wereintroduced in the 3678s.

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    THEORY

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    HOW DOES A PRISM WORK?

    0ight changes speed as it moes

    rom one medium to another #orexample, rom air into the glass othe prism$. This speed changecauses the light to be reracted andto enter the new medium at a

    di%erent angle #uygens principle$.The degree o bending o the light)spath depends on the angle that theincident beam o light maes with

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    the surace, and on the ratiobetween the reractie indices o

    the two media #Snell)s law$. Thereractie index o many materials#such as glass$ aries with thewaelength or color o the lightused, a phenomenon nown as

    dispersion. This causes light odi%erent colors to be reracteddi%erently and to leae the prismat di%erent angles, creating ane%ect similar to a rainbow. This can

    be used to separate abeam owhite light into its constituentspectrum o colors. Prisms willgenerally disperse light oer amuch larger requency bandwidth

    than di%raction gratings, maingthem useul or broad9spectrumspectroscopy. +urthermore, prismsdo not su%er rom complications

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    arising rom oerlapping spectralorders, which all gratings hae.

    Prisms are sometimes used or theinternal refection at the suracesrather than or dispersion. I lightinside the prism hits one o thesuraces at a su:ciently steep

    angle, total internal refectionoccurs and all o the light isrefected. This maes a prism auseul substitute or a mirror insome situations.

    Angle of Minimum Dei!"ion

    The minimum alue o angle odeiation, is called angle ominimum deiation. It isrepresented by the symbol ;m.

    +or same angle o deiation #;$there are two alues o angle oincidence. 1ne alue equals

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    other alue equals =e< !s angle =i< isincreased rom a small alue, =ehenangle o deiation isminimum#;m$, then, =i< and =e