Optics

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 Wave optics

First what is wave optics ?

Ray optics means reflection or refraction of light and what is a light that mean we have to study what is a light ?

Newton proposed a theory  :- 

Corpuscular nature of light
 
Corpuscular means a particle of light 

1)  Hard , elastic and massless .
 
2)  They travel with high speed in the vacuum and else .
3)  Different colours due to different shape and size .

He explained that speed of light in denser medium is higher than in rarer medium .

Vd  >  Vr    ( explained by Newton ) 

It was WRONG. It was drawback of Newton's corpuscular nature of light  .

He couldn't explain polarization interference and diffraction .
He explained  refraction and reflection of light .

Theory by Huygens  (Wave Nature)

He explained that wave is a mechanical wave .
Different colours due to different wavelength .
Could explain reflection , refraction , interference , and diffraction .

Result obtained -  Velocity of light in denser medium is less than velocity of light in rarer medium .

Vd  <  Vr  ( Corrected by Huygens ) .

It couldn't explain Photoelectric effect and Compton effect .
 
Presence of hypothetical medium Ether could not be proved .

Maxwell said that light is an Electromagnetic wave .
Primary sources are sun , star , tubelight.

 The sources which emits the light itself is called as a primary sources .
Secondary sources are wall moon wall .

Secondary sources are sources which do not emits light sources .

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