Wave optics

  Lesson No 07. Waves Optics

Introduction: We have studied in class XI that light travels in a straight line which was considered to be in the form of ray.In the form of ray light shows various phenomenon like Reflection,Refraction,Dispersion. In previous class we have studied about reflection of light  through spherical mirrors and refraction through lens and many more thing about optical instruments. In this chapter we are going to discuss about Propagation of light in surrounding ,its various properties in the form of a waves.

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Various theory related to light

Earlier we studied light to be in the form of ray which travels in straight line i.e One -dimensional Motion.The shadows,images were the result of light having linear motion. based on this ray R Discartes s studied particle nature of light which was further proposed by Newton in 1636.

Newton's Corpuscular Theory

1. Every light source emits large number of minute particles which was termed as 'corpuscles'that travels in a straight line without any  external force.
2. This particle was elastic,rigid,massless and travels with high speed which vary from medium to medium.
3. The different size of the corpuscles corresponds to different colour of light.
4. When this particle fall on our retina its creates sensation of light.

This theory could satisfactorily expain reflection,refraction and inverse square law but had some drawbacks:

1. Partial reflection and refraction was not explained by  this theory
2. this theory predicted that speed of light  in denser medium is larger than rarer medium which was proved wrong by Focault.

_{│Huygens Wave Theory>>>│} 

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