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NAVODAYA VIDYALAYA SAMITI

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CHAPTER -11��LIGHT, SHADOWS AND REFLECTIONS

CLASS :- VI

SUBJECT :- SCIENCE

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OBJECTIVE�Children will be able to

  • Define keywords of the chapter.
  • Sort different objects on the basis of emission of light and crossing the light through objects .
  • Understand the process of formation of shadow and its criteria.
  • Make their own pinhole camera.
  • Perform different activities related to light shadows and formation of images.

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TOPICS TO BE COVERED

  • Light
  • Luminous and non luminous object
  • Transparent , translucent and opaque objects
  • Shadow
  • Pinhole camera
  • Mirrors and Reflections

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WHAT IS LIGHT?

  • Light is a form of energy which enables us to see.
  • It travels on a straight line.
  • It shows rectilinear motion.

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LUMINOUS OBJECTS :-

Luminous objects give out or emit light of their own.

Eg:- sun, lamp, candle, torch, electric light, glow worm etc.

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NON-LUMINOUS OBJECTS :-

  • Non-luminous objects do not give out or emit light of their own.
  • Eg:- door , eraser, paper, notebooks , plastics etc.

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What about our planet?

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ACTIVITY

  • Collect the objects like a pencil , an eraser ,plastic scale , metal scale , tracing paper , single sheet of paper , clean glass tumbler. Now try to look through these objects one by one. Do you able to see through all objects you gathered . Record your observation in a given below table.

Objects/Materials

View through the objects(fully/partially/

not at all)

object is opaque/transparent/

translucent

 A pencil

 Not at all

 opaque

 Plastic scale

partially 

 translucent

 Clean glass tumbler

 fully

 transparent

 

 

 

 

 

 

 

 

 

 

 

 

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TRANSPARENT, TRANSLUCENT AND OPAQUE OBJECTS :-

a) Transparent objects :- Objects through which we can see clearly.It allows most of the light to pass through it.

Eg:- clear glass, clear water, some plastics, air etc.

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B) TRANSLUCENT OBJECTS :- Objects through which we can see but not clearly . It allows some light to pass through it.�Eg:- tracing paper, some plastics, muddy water etc.

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C) OPAQUE OBJECTS :- Objects through which we cannot see at all.It does not allow any light to pass through it.� Eg :- wood, rubber, some plastics, metals like iron, aluminium, copper etc.

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SHADOWS :-

A shadow is formed when an opaque object is placed in the path of light. It is an area of darkness.

A shadow of an object can be seen only on a screen. The ground, walls of buildings etc. act as a screen for shadows.

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Sometimes the shadow of an object gives us information about the shape of the object.

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  • Sometimes shadows can also mislead us about the shape of the object . It does not give information of the colour of the object.

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  • Opaque objects make a dark shadow.
  • Translucent objects produce a weak shadow.
  • Transparent objects do not produce a shadow at all.

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PINHOLE CAMERA :-

  • A pinhole camera is a device which helps us to see images of objects.
  • It has a box with a pinhole at one side and a screen at the other side. The light from the object passes through the pinhole and forms an inverted image of the object on the screen.

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HOW TO MAKE PINHOLE CAMERA

  • Take two boxes so that one slide into another with no gap in between them.
  • On the front face of the larger box make a small hole in the middle.
  • In the smaller box ,cut out a square with a side about 5 to 6 cm from the middle.
  • Cover the open square with tracing paper.

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  • Slide the smaller box inside the larger one with the hole , in such a way that the side with the tracing paper is inside.

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  • Now the camera is ready.

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PINHOLE IMAGE OF THE SUN :-

We can see a pinhole image of the sun by using a large sheet of cardboard having a pinhole in the middle. Hold the cardboard in sunlight and let its shadow fall on a clear surface. A small circular image of the sun is seen in the middle of the image of the cardboard.

This pinhole camera can be used to see the image of the sun during solar eclipse.

We should never see the sun directly because it can cause damage to our eyes.

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  • ��The gaps between the leaves act as a pinholes . These gaps are all kinds of irregular shapes but we can see circular images of the sun.

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ACTIVITY :- To show that light travels in straight line :-

Light a candle and fix it on a table. Take a piece of straight pipe or a rubber tube. Look at the candle through the pipe. You can see the candle flame. If the pipe is bent, you cannot see the candle flame. This shows that light travels in a straight line.

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MIRRORS AND REFLECTIONS :-

a) Mirrors :- are used to see reflections of objects. We can see reflections of our face and other objects in a mirror.

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b) Reflection of light :- When light falls on a mirror the direction of light changes. This is called reflection of light.

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Due to reflection of light images are formed.

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Now do you understand what are shadows and images?

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Web links to explore your knowledge

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Credit for related photos /videos/content

  • www.google.com/search

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THANK YOU!