• Light travels along a straight line.
  • The speed of the light is 3*10 to the power 8 m/s.
  • When light falls on a smooth/shiny surface the light gets reflected back at the same angle.


Reflection Of Light:

  • The surface of water acts like a mirror and change the path of light.
  • The change of direction of light at an angle is called reflection of light.
  • On a rough surface  the light rays gets scattered.
  • An image formed by the plane mirror is erect and is of the same size as that of the object.
  • The image on the screen which could not be obtained by a plane mirror is called a Virtual Image.
  • White light is composed of seven colours- Red, Orange, Yellow, Green, Blue, Indigo and Violet.

Spherical Mirror:

  • Spherical mirror is a curved mirror.
  • Spherical mirrors are both concave and convex.
  • Concave mirror is also known as converging mirror.
  • Concave mirror reflects the light towards inward to one focal point.
  • Convex mirror is also known as the diverging mirror.
  • Convex mirrors can form images of objects spread over a larger area.
  • The outer side of the convex mirror is reflecting.
  • The image formed by the concave mirror can be smaller or larger in size then the object.
  • The image may also be real and virtual.

Uses Of Concave Mirrors:

  • Doctors use concave mirrors to examine our eyes, ears etc..
  • Dentists use concave mirrors so that they get the enlarged image of the teeth.
  • Headlights of cars and scooters are concave in shape.
  • Astronomical Telescopes have concave mirrors.
  • Concave mirrors are used in shaving mirrors.

Uses Of Convex Mirrors:

  • Convex mirrors are used in traffic lights.
  • Convex mirrors are used as the rear view mirror in vehicles.
  • Convex mirrors are used inside buildings.
  • Magnifying glass have convex mirrors inserted in it.
  • The sunglasses which we use are also made up of convex mirrors.


  • A transparent material with curved sides for dispersing light rays is known as Lens.
  • Lenses are widely used in spectacles, telescopes etc..
  • The lenses which are thicker in the middle than at the edges are convex lenses.
  • Convex lenses are also called as converging lens.
  • The lenses which are thinner in the middle than at the edges are concave lenses.
  • The concave lenses are also called as Diverging Lens.
  • We can see the image formed by the lens from the side opposite to that of the object.
  • The image formed by a convex lens can be real, inverted or virtual ,erect.
  • However the image formed by the Concave lens is always erect, virtual and smaller than the object.

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