Optical physics 

Introduction of Geometrical Optics

Geometrical Optics is the Study of light in which light is considered as moving along a straight line. When light meets a surface which seperates two media, reflection and refraction takes place. 

  1. Since the wavelength of light

    𝜆 = 500nm very small, so the behavior of a light beam passing through apertures could be handled by geometrical optics.
  2. The appearance of distinct shadows influenced Newton to assert that the apparent rectilinear propagation of light was due to stream of light bunch of particles rather than a wave motion. 

 Newtons Corpuscular Theory(1675)

  • Every light source emits tiny particles called corpuscle (elastic, rigid & massless, different shape and size).
  • Corpuscles travel in straight line. corpuscle travel with different speed in different medium. Speed of light is greater in denser and slowest in rare.
  • Different colors of light have different shape & size for corpuscles.
Huygens Wave theory of light (1678)

  • Christian Huygens argued that light might be some sort of wave motion.
  • Huygens principle is a geometrical construction for determining the position of the new wave at some point based on the knowledge of the wave front that preceded it.
  • All points on a given wave front are taken as point source for the production of spherical secondary wave, called wavelets, which propagate outward through a medium with speed characteristic of waves in that medium.

Reflection of light

A ray of light, the incident ray, travel in a medium when it encounter a boundary with a second medium, part of the incident ray is reflected back into the first medium.
                                
Reflection of light
Refraction of Light

  • when a ray of light traveling through a transparent medium encounters a boundary leading into another transparent medium, part of the energy is reflected and part enter the second medium.
  • The ray that enters the second medium changes its direction of propagation at the boundary.
  • This bending is called Refraction.
    Refraction of light