Light

Start music   Jan 11 2017 || 1:21 PM

Properties of light

  • Light travels along a straight line
  • The change in the direction of light by a mirror is known as reflection of light

 

Image

  • The reflection of an object which appears behind the mirror is called an Image

 

Spherical mirrors

  • If the reflecting surface of a spherical mirror is concave, it is called concave mirror
  • If the reflecting surface of a spherical mirror is convex, it is called convex mirror

 

Real and Virtual images

  • The image of an object formed on a screen is called a real image
  • An image of an object when cannot be obtained on a screen, it is called virtual image

 

Images on plain mirror

  • The left side of the object is seen on the right side in the image,
  • The right side of the object appears to be on the left side in the image
  • This is called as lateral inversion

 

Images on concave mirror

  • They maybe smaller or larger in size than the object
  • They may be real or virtual
  • When the object is placed very close to the mirror, the image formed is virtual, erect and magnified

 

Images on convex mirror

  • The images are always erect, virtual
  • They are always smaller than the object

 

Uses of concave mirrors

  • Doctors use for examining eyes, ears etc
  • Dentists use to examine teeth
  • Reflectors of torches, headlights of vehicles use concave mirrors

 

Uses of convex mirror

  • Convex mirrors can form images of objects spread over a large area.
  • So, they are used in making rear view mirrors for vehicles

 

Lenses

  • Lenses are widely used in spectacles, telescopes and microscopes
  • Convex lens converges the light falling on it. Hence it is called as converging lens
  • Concave lens diverges the light and so it is called as diverging lens

 

Images formed by convex lens

  • Images formed by convex lens can be real and inverted
  • When the object is placed very close to the lens, the image formed is virtual, erect and magnified
  • When used to see objects magnified, the convex lens is calleda magnifying glass

 

Images formed by concave lens

  • Images formed by concave lens are always virtual, erect and smaller than the object

 

Sunlight/White light

  • The sunlight composes of 7 colours: red, orange, yellow, green, blue, indigo and violet
  • Together they appear white
  • They can be split by using a glass prism