Phenomena of light

• Light


  A type of electromagnetic radiation that allows the human eye to see or makes objects visible
• Light


  • When it penetrates the Earth's atmosphere, it causes phenomena such as the formation of rainbows, blue skies, reddish sunsets and white cloud formation
• Plane mirror


  A mirror with a flat reflective surface
• Plane mirror


  • For light rays striking a plane mirror, the angle of reflection equals the angle of incidence
  • The angle of the incidence is the angle between the incident ray and the surface normal
• Spherical mirror


  A mirror with a curved reflecting surface
• Types of spherical mirrors

  • Convex
  • Concave
• Convex mirror


  • Bulges outward
  • Shows things the right way up and smaller
• Concave mirror


  • Hollowed inwards
  • If the object is close, the image appears bigger and right way up
  • If the object is further away, the image may look smaller and inverted
• Reflecting surface of a spoon

  • Outer bulging part acts like a convex mirror, shows an upright and smaller image
  • Inner hollowed part acts like a concave mirror, shows an inverted, smaller image
• Selective reflection and selective transmission


  The colors of the object we see depends on its ability to reflect or to transmit the light incident to it, which is dependent on the object's natural vibrating frequencies
• Opaque object


  • Allows no light through it
  • Some of the frequency of the visible light is absorbed, while others reflected
• Transparent object


  • Allows all light rays to travel through them
  • Some of the frequencies of light are absorbed while allowing some to pass through
• Refraction


  The bending of light as it passes through mediums of varying density, due to light speeding up or slowing down
• Optical illusions due to refraction

  • Mirage
  • Rainbow
  • Halos around the sun or moon
• Formation of mirage


  1. Heating of the ground during hot sunny days results in a temperature gradient in the air

  2. Light coming from the sun is bent due to the varying optical density

  3. Our brain perceives the bent light as coming from the ground, creating the illusion of a puddle of water
• Formation of rainbow


  1. Light enters a water droplet, is refracted and dispersed into the spectrum of colors

  2. Total internal reflection occurs at the back of the water droplet

  3. Light then exits the water-air interface, where refraction takes place once more

  4. The dispersed colors are seen as a rainbow
• Seeing a rainbow


  • There must be suspended water droplets in the sky
  • The light source should be behind the observer
  • Only those water droplets before the observer that are on a 42-degree circle centered about the antisolar point can give a concentrated rainbow light
  • Each observer sees a different rainbow, as they receive scattered light from different sets of water droplets
• Secondary rainbow


  • Formed when light undergoes two total internal reflections and refractions within a water droplet
• Supernumeraries


  • Thin, pastel-colored bands or fringes appearing below the primary rainbow, adjacent to the violet band, due to interference of light
• Halo formation


  • Light refracts from hexagonal ice crystals present in cirrus clouds, acting like prisms with a cross-section of an equilateral triangle
  • The most common halo has an angular radius of 22 degrees
• Sundog or mock sun


  White or colored patches of light to one or both sides of the sun, caused by light refracting through horizontally oriented hexagonal ice crystals in cirrus clouds

  Also known as parhelia which means the sun.