light

• Light


  Form of energy that causes the sensation of vision

  without light we won’t be able to see anything
• Properties of light

  -form of energy

  -travels along a straight line

  -doesnt need a medium for its propagation

  -can travel through vacuum

  -light in different colors have different wavelength and frequencys
• How light helps us to see

  Rays of light reflect or bounce off, objects just like a ball bounces on the ground.this reflection of light is what enables us to see everything around us
• incident ray


  Ray of light that straight way falls on the reflecting surface from the object or a source
• Reflected ray


  Ray of light that is supposed to be reflected back after striking the reflected surface
• Angle of Incidence 


  angle btw incident ray and the normal
• Angle of reflection 


  Angle btw reflected ray and the normal
• Law of reflection

  Incident ray,reflected ray,normal lie in the same place

  —>angle of incidence is equal to angle of reflection

  
• Normal(imaginary line)(dotted)


  Straight line perpendicular to the reflecting surface that acts as a separation btw the plane of incident and plane of reflection
• When an image is reflect in a plane mirror the image is:

  Same size as the object

  latterly inverted

  virtual

  same distance behind the mirror as the object is in-front of if
• How does an image form in a plane mirror

  Virtual,erect,same size as object,image seems equidistant from the mirror
• refraction of light

  Phenomenon of change in the path of light in going form one medium to another

  E.g a pencil immersed in water appears bent at the interface of water
• Emergent ray 


  Ray that passes through a refracting surface and emerged on the other side
• Refraction

  60 at end is emergent ray

  
• Reflection

  Change of direction of a ray when it strikes a surface without passing through it
• Ray box


  Apparatus used to produce a ray of light
• optically rarer medium


  speed of light is more
• optically denser medium


  speed of light is less
• in going from rarer to denser medium ,the ray of light does what towards normal

  bends
• from denser to rarer

  ray of light bends away from normal , reflected angle is greater than angle of incidence
• when light not refract


  light wave approaches the boundary in a direction that is perpendicular to it

  
• angle of deviation


  angle between the direction of the incident ray and the emergent ray

  
• critical angle


  angle of incidence for which the angle of refraction is 90 degree

  
• refractive index


  measures speed of light when it passes into a medium from air

  n=c\v n=refractive index c= speed of light in

  vacuum(3X10^8m\s)

  v=speed of light in medium
• important about refractive index!!(RI)

  -Speed of light is 1.5 times slower in glass than vacuum as air is less dense thsn gas

  -if medium is denser RI is greater than 1

  -if medium is less dense RI is less than 1

  -RI has no unit
• Coating


  • Protective layer for the core and cladding
  • Has a higher index of refraction than the core and cladding to prevent unwanted light from refracting
• Deviation of light through prism

  Light changes direction and bends when passing from air to the glass of the prism due to differences in refraction index
• Core

  • Provides a pathway for light to travel
• Components of each optical fiber strand


  • Core
  • Cladding
  • Coating
• Cladding

  • Holds the light inside the core and controls the direction in which light is spread through the fiber
  • Allows for total internal reflection when light enters at the critical angle
• Prism is a homogeneous, solid, transparent, refracting medium bounded by two plane surfaces inclined at an angle
• When white light is passed through a glass prism, it splits into its spectrum of colors (violet, indigo, blue, green, yellow, orange, red) in a process called dispersion
• Uses of Optical fiber

  • Medicine
  • Endoscope for internal body viewing
  • Telecommunication services like internet, television, and telephones
• Total internal reflection

  1. Light is in the more dense medium and approaching the less dense medium

  2. Angle of incidence is greater than the critical angle
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• Converging lens , convex

  Thick from inside

  thin from outside

  lens that causes rays of light parallel to axis to converge at principle focus
• Diverging rays,concave


  Thick from outside

  thin from inside

  Lens that causes rays of light parallel to the axis to diverge from the principle focus