Chapter: Light

• What makes things visible
  • Need for light reflecting off objects
  • Entering our eyes
• Laws of Reflection
  • Incident ray: Ray striking the surface
  • Reflected ray: Ray bouncing back
  • Normal: Perpendicular line at the point of incidence
  • Angle of incidence ($\angle i$): Angle between incident ray and normal
  • Angle of reflection ($\angle r$): Angle between reflected ray and normal
  • First Law: $\angle i = \angle r$
  • Second Law: Incident ray, normal, and reflected ray lie in the same plane
• Regular vs Diffuse Reflection
  • Regular reflection
    • Occurs on smooth/polished surfaces (e.g., plane mirror)
    • Parallel rays remain parallel
    • Forms clear images
  • Diffuse (Irregular) reflection
    • Occurs on rough surfaces (e.g., cardboard, wall)
    • Parallel rays scatter in different directions
    • Illuminates objects without forming sharp images
• Multiple Images
  • Produced by two or more mirrors inclined at an angle
  • Formula for number of images: $n = (360^\circ / \theta) - 1$
  • Applications: Kaleidoscope, Periscope
• Sunlight - White or Colored?
  • Sunlight is white light composed of seven colors
  • Dispersion: Splitting of white light into its component colors
  • Example: Rainbow formation (water droplets act as tiny prisms)
• Structure of the Human Eye
  • Cornea: Transparent front window, refracts light
  • Iris: Colored part that controls the amount of light entering
  • Pupil: Opening in the iris; adjusts size based on light intensity
  • Lens: Focuses light rays onto the retina
  • Retina: Light-sensitive screen containing photoreceptors
    • Cones: Sensitive to bright light and colors
    • Rods: Sensitive to dim light
  • Optic nerve: Transmits visual signals from retina to the brain
• Care of the Eyes
  • Wash eyes clean with regular water
  • Avoid reading in too dim or too bright light
  • Do not look directly at the Sun or powerful laser
  • Maintain a proper distance while reading
  • Include Vitamin A rich foods in diet (carrot, broccoli, eggs, milk)
• Visually Impaired Persons
  • Can read and write using the Braille system
  • Developed by Louis Braille
  • Uses raised dots on a special paper representing letters and numbers
  • Read by touching with fingers