LIGHT SHADOWS AND REFLECTION

  • LUMINOUS MATERIALS:The Materials which emit their own light are called luminous objects.Eg. The sun

  • NON-LUMINOUS MATERIALS:The Materials which do not emit their own light are called non-luminous objects.Eg.The Moon , it doesn’t not emit its own light instead it reflects the light from the sun.

  • In ancient times people used oil , stones or sticks to make fire , or even animal fat to make light .

  • LIGHT EMITTING DIODE (LED):They are Modern light sources that consume much less power , are brighter and last longer than traditional lamps , they are also better for the environment and reduces electricity bill.

  • PROPERTIES OF LIGHT:

  • Light travels in a straight line.Eg. If we see a candle through a hollow pipe we see light but we bend the pipe then light will not pass through .

  • Light reflects.Eg. The sun reflects its light on the Moon , the Earth and other planets .

  • Light acts like energy packets.Eg. we get Vitamin D from staying in sunlight(light).

  • The Colour of Light is decided by the frequency .

  • Light travels faster than sound.Eg. Someone’s voice will reach our ears slower than Sunlight ( rays or beams or light from sun )

  • TYPES OF MATERIALS:

  • Transparent materials are the materials which allow light to pass through them completely.Eg.Glass,Window etc.

  • Translucent materials are the materials which allow light to pass through them partially.Eg.Tinted Glass,Butter Paper etc.

  • Opaque materials are the materials which don’t allow light to pass through them at all.Eg.Wood,Cardboard etc.

  • SHADOW:When an object blocks light from falling on the screen , the dark patch that is formed is known as a shadow.

  • NECESSITIES FOR SHADOW FORMATION:

  • A Screen : A wall (any opaque object )

  • A source of light: A lamp or a torch

  • An object : A ball ( any opaque object )

  • REFLECTION OF LIGHT: The change in the direction of light by a shiny surface like a mirror is called reflection of light.

  • The picture formed on the Mirror is known as the image.Eg. The pen which appears behind the mirror is the image of the object( here, pen).

  • The thing of which there is reflection is itself the object.Eg.the example given above , the pen was the object.

  • An upright image is called an erect . They are formed in plane mirrors.

  • A left-right reversal is called lateral inversion.Eg. when our left appears right and right appears left it is laterally inverted.

  • PINHOLE CAMERA: A pinhole camera is a device in which light rays from an object pass through a tiny hole(pin hole) and form an image on the screen.

  • PERISCOPE: It is a device that has two plane mirrors which helps us see objects now clearly visible or far away . The object forms an image on the first plane mirror then the image from the first plane mirror is reflected onto the second plane mirror from which we then see . They are used in submarines and tanks to see objects far away or not clearly visible .

  • KALEIDOSCOPE: It is a device that consists of three plane mirrors which form beautiful symmetrical patterns due to reflection of light . We see colourful reflections due to multiply colourful beads present inside the kaleidoscope .