FIBRE TO FABRIC Class VII Chapter III (C.B.S.E.)

FIBRE TO FABRIC      Class 7      Chapter 3 (C.B.S.E.)

Introduction-The very thin strands of the thread is called fibre. Fibres are soft and they can be spun to form yarn or thread. The yarns are then woven to form the fabric i.e. clothes. The fibres are obtained from plants as well as from animals. Plant fibres are – cotton, jute, hemp, coir, some grasses fibres, linen from flax, bamboo, nettle etc. The hairs of animals called ‘fleece’ are used as fibres. The animal fibres are- Silk, Sheep Wool, Angora goat wool, camel hair, rabbit hair etc.

The plant and animal hairs are natural fibres while synthetic fibres are also there which are prepared in factories. e.g.- Rayon, Nylon, Polyester, Plastic, Acrylic etc.

Animal Fibres- Wool and Silk- Wool and silk are two well known animal fibres. The wool keep the animals warm in cold and protect from insect bites. The hairs (wool fibres) on the skin of sheeps are of two types- (i) outer coarse beard hairs and (ii) fine soft under-hairs close to skin.

The better quality sheeps like those having more soft under-hairs are selected for reproduction (or breeding) to form better quality of wool. This process is called ‘selective breeding’. The wool is obtained from different varieties (breed) of sheeps, Yaks, Angora Goats, Pashmina goats, Camel, Llama, Alpaca, Rabbits etc. Yaks are found in Himalayan regions like Ladakh, Nepal, Bhutan, Sikkim, Arunachal Pradesh, Tibet etc. Angora and Pashmina Goats are found in Jammu and Kashmir of India. The famous Angora wool is obtained from Angora goats. Pashmina shawls are prepared from the wool of Pashmina goats. Llama and Alpaca are South American wool yielding animals.  

                                                                                                                                                                                                                           

Yak

Converting Fibers to wool- The rearing and breeding of sheep is a good source of income. The hair of sheep is cut and different methods are adopted to get the wool. Lets us know it in details.

(a) Rearing and breeding of Sheeps- The sheeps are herbivores. They prefer grazing of grass, leaves, jowar, bajra, pulses, oil cakes etc. In summer season you must have seen the shepherds grazing the sheeps. In winter sheeps are kept indoors. Good quality wool are obtained from improved variety of sheeps. In India the common breeds of sheeps are-

S.N.	Breed Name	Quality of Wool	Location
1	Bakharwal	Good for shawls	Jammu and Kashmir
2	Lohi	Good quality wool	Rajasthan , Punjab
3	Nali	Carpet wool	Rajasthan, Punjab, Haryana
4	Rampur Bushair	Brown coloured hairs	Uttar Pradesh, Himachal Pradesh
5	Marwari	Coarse wool	Gujarat
6	Patanwari	For hosiery cloths	Gujarat

  (b) Processing of Fibres into wool-The making of wool yarn for preparing sweaters and shawls is a long process. This process can be simply divided into following six steps for convenience of study.

Step 1. Shearing- The cutting of the fleece of sheep along with dead outer skin is called as shearing. It is just like shaving of beard and cutting of hairs of ours. It does not harm the sheeps.

Step 2. Scouring- The sheared skin may contain dead skin, dust, dirt and grease. The through washing to remove dead skin, dust, dirt and grease is called as scouring. Earlier scouring was done in water tanks by stirring but scouring is nowadays done by machine.

Step 3. Sorting- The cleaned hairs (fleece) are sent to factories to sort out (separate) the hairs of different texture –length and thickness. This process is called as sorting. 

Step 4. Re-scouring and Resorting to Pickup Burrs- The sorted hairs are again cleaned i.e. scoured and dried. The small fluffy hair fibres called burrs are picked out i.e. sorted out. The remaining good fibres are ready to be drawn into yarns.

Step 5. Dyeing- The woolen fibres can be dyed in different desired colours as the colour of natural wool is black, brown or white.   

Step 6. Rolling into yarns- The woolen hairs fibres are straightened, combed and rolled into yarns. The shorter fibres are spun and woven into woolen cloths while the longer fibres are rolled into yarns for woolen sweaters, mufflers, cap etc.

Sorter’s Disease as an occupational hazard- The workers working in wool industry sometimes get infected by a fatal disease called ‘Sorter’s disease’. It is a blood infection caused by Anthrax bacteria.

Silk- Silk is a natural fibre obtained from silkworms. Silk is a protein secretion by the silkworm or larva or caterpillar. The protein secretion forms cocoon from which silk fibre is extracted. Silk yarns are different in texture i.e. they may be coarse, smooth or shiny. There are different kinds of silk found in India. e.g. - Tassar, Mooga, Kosa, Eri, Mulberry etc. The silk fibres are smooth, lustrous, and elastic. Silk fibres can be dyed to impart different colours. Silk fibres are very strong. The silk is costly so the artificial silk ‘rayon’ is used in place of natural silks.      

Sericulture- The rearing of silkworms to get silk is called sericulture. The soft leaf of mulberry tree (Morus alba) are usually used to grow the caterpillar.

Life cycle of Silk moths- The male and female silk moths reproduce to lay eggs on leaves. The male silk moth is smaller than the female silk moth in size. The eggs hatch to form the larva/caterpillar/ silkworm. The caterpillar grows in size and starts forming a net like structure made up of protein fibres. Protein fibres dry up quickly. The shape of caterpillar becomes like figure of eight (8). The reserve food helps in this stage of development called Pupa stage. The covering over pupa is called cocoon. The Silk fibre is extracted from the cocoon using the sunlight or boiled water or steam.  

Life history of Silk moth

 

Cocoons

Caterpillar / Silkworm

                                            

Converting silk fibres of Cocoon to form silk- The silk moths are reared to collect their cocoons from which the silk fibres are obtained.  

(a) Rearing of Silkworm to get cocoons- Hundred of eggs are laid by the female silk moth at a time. The eggs are carefully stored on strips of paper or cloth. The suitable temperature, humidity and hygienic conditions are necessary for developing the eggs. The eggs hatch to form caterpillar/larva/ silkworm that eats day and night and enormously increase in size. The caterpillars are kept in clean bamboo trays and given freshly chopped mulberry leaves. After 25-30 days the caterpillars stop eating mulberry leaves and transform themselves in pupa stage as like shape of 8 inside cocoons. Cocoon is protein secreted by caterpillar around it.  

(b) Processing of silk fibres of cocoon (reeling of the silk) to form silk- the cocoons are put in boiled water or under the sunlight or exposed to steam to separate the silk fibres. The process of extracting the silk fibres from the cocoon is called reeling. Reeling is done by special machines which unwind the silk fibres from the cocoons. The silk fibres are then converted to silk yarns. The silk yarns are used to prepare silk clothes by weavers.

                                                  EXERCISE QUESTIONS-SOLVED

Q.1 You must be familiar with the following nursery rhyme:

(i) ‘Baa baa black sheep, have you any wool.’

(ii) ‘Mary had a little lamb, whose fleece was white as snow.’

Answer the following:

(a) Which parts of the black sheep have wool?

(b) What is meant by the white fleece of the lamb?

        Ans- (a) Wool is obtained from the hairy fibres of the sheep.

                 (b) The white fleece of the lamb denotes it’s white hairs.

       Q.2 The silkworm is (a) a caterpillar,  (b) a larva. Choose the correct option.

       (i)  a                    

      (ii) b                      

      (iii) both a and b               

      (iv) neither a nor b

       Ans-Both a and b

       Q.3 Which of the following does not yield wool?

       (i) Yak                

       (ii) Camel             

      (iii) Goat                             

      (iv) Woolly dog

       Ans- (iv) Woolly dog

      Q.4 What is meant by the following terms?

       (i) Rearing          (ii) Shearing        (iii) Sericulture

 Ans- (i) Rearing- All the activities involved in breeding and raising up of animals is called rearing.

(ii) Shearing –The process of shaving off of the fleece of wool producing animals is called shearing. It is done by scissors or machines. Dead outer skin may also come along with shaved hairs.

(iii) Sericulture-The rearing of silkworms to get silk is called sericulture.    

 Q.5 Given below is a sequence of steps in the processing of wool. Which are the    missing steps? Add them.

       Shearing, ……………., Sorting, ……………….., …………….., …………………

      Ans-scouring, re-scouring, dyeing, spinning

Q.6 Make sketches of the two stages in the life history of the silk moth which are    directly related to the production of silk.

      Ans- Draw figures of larva (caterpillar/Silkworm) and  Pupa.

Q.7 Out of the following, which are the two terms related to the silk production?

       Sericulture, Floriculture, Moriculture, Apiculture, and Silviculture.

Hints: (i) Silk production involves cultivation of mulberry leaves and rearing      silkworms.

 (ii) Scientific name of mulberry is Morus alba.

        Ans- Sericulture and Moriculture

      Q.8 Match the words of column I with those given in column II:

      Column I                        Column II

   1. Scouring                         (a) Yields silk fibres

   2. Mulberry leaves              (b) Wool yielding animal

   3. Yak                                  (c) Food of silk worm

   4. Cocoon                            (d) Reeling

                                               (e) Cleaning sheared skin

      Ans- 1.-V     2.-C      3.-Wool yielding animals       4.- Yields silk fibres

Q.9 Given below is a crossword puzzle based on this lesson. Use hints to fill in the blank spaces with letters that complete the words.

           Down (D)                                                           Across (A)

       1. Thorough washing                                1. Keeps warm

       2. Animal fibre                                           2. It’s leaves are eaten by silkworms

       3. Long threads like structure                3. Hatches from egg of moth

       Ans

						1D		2D
			3D		1A
2A
3A

 

        Ans- 1A- Wool                    2A- Mulberry                3A- Caterpillar

                 1D- Scour                   2D- Silk                           3D- Fibre

 

 

 

CHECK YOUR PROGRESS      Time= 40 Minutes     Total Marks= 15

Q.1 What are the steps involved in processing of wool to prepare yarns?

Q.2 Describe the life-cycle of silk moths with a suitable diagram.

Q.3 Describe the steps in silk moths rearing to reeling of silk fibres.

GROUP PROJECTS –

1. Collection of silk made clothes. It’s history of making and traditional instruments used in making of silk clothes.

2. Collection of organisms of different stages in the life cycle of Silk moths.

3. Draw a labeled diagram of life cycle of silk moths and explain each stage.

4. Locate silk routes on the physical map of Asia. Write the history of origin of silk cloths making.

5. Visit a local Sericulture site and experience the making of silk yarns and silk clothes.

          

 

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LIGHT, SHADOWS AND REFLECTIONS

  LIGHT, SHADOWS AND REFLECTIONS

              Chapter 11 Class VI (C.B.S.E./NCERT)              

 

Key Learning Points-Introduction, Sources of light, Luminous and Non-luminous objects, Transparent, Translucent and Opaque Objects, Straight pathway of Light, Shadow, Differences between shadow and image, A Pinhole Camera, Mirror and Reflection of Light

Learning Objectives- At the end of this lesson the students will be able to-

1. To understand about luminous and non-luminous objects

2. To know about transparent, translucent and opaque objects

3. To understand shadow formation conditions,

4. To differentiate between shadow and image

5. To have skills to prepare pinhole camera and use a pinhole camera

6. To understand straight pathway of light

7. To know refection of light and re-reflection by mirrors.

Introduction- Light plays a very crucial role in our daily life. Light is a form of energy that gives sensation of vision to our eyes. Except the time of sleeping we require light to do almost every work. Light is produced by light emitting sources called luminous objects. Light can completely pass through transparent objects, partially pass through translucent objects and do not pass through opaque objects. Shadow is formed on screen by opaque objects when light falls on it. Shadows are dark coloured, smaller or larger than the object. In a plane mirror, image of an object is laterally inverted, same colour, size and formed in front of object in mirror. A Pinhole camera is used to indirectly see the bright objects like the Sun. Light always travels in straight pathway. Mirrors reflect the light falling on them.      

Sources of Light- The light is produced by natural as well as artificial (man-made) objects. e.g.- The Sun, The Stars, Fireflies or glow-worms (or Jugnu) are some of natural sources of light. e. g.-The glowing electric bulb, the burning candles, burning matchsticks are examples of artificial sources of light.

Luminous and Non-luminous objects-The objects which give out light of their own are called luminous objects. e.g.- The Sun, The Stars, Fireflies or glow-worms, The glowing electric bulb, the burning candles, burning matchsticks etc. The brightness of a luminous object decreases as we move away from it.

                                                            

The objects which do not produce light of their own are called non-luminous objects. e.g.- The planets, moon, books, bench, desk, etc.

Transparent, Translucent and Opaque Objects- Those objects through which light can pass completely are called transparent objects. e.g.- Air, Clean Water, Clear glass, spectacles etc.

Those objects through which light can partially pass are called translucent objects. e.g.- Muddy water, smoky glass, oiled paper, milk etc.

Those objects through which light cannot pass are called opaque objects. e.g.- Stone, book, Wooden furniture, Rubber ball etc.   

Straight pathway of Light- The light travels always in linear or rectilinear or straight pathway. e. g. The light coming out of a torch, motor car, The Sun etc. The Sunlight propagates from the Sun to the Earth. But, its direction changes due to air. The direction of light hardly changes in air for short distances. 

Shadow-The dark coloured patch formed on the screen opposite to the light by an opaque object is called shadow. For the formation of a shadow, a source of light, an opaque object and a screen are required. Shadow is formed by an opaque object when light falls on it. Its size and shape change according to direction of light or orientation of object. It can be large or small than the object. During morning and evening shadow is larger. It is smaller during noon. The colour of shadow is dark irrespective of the colour of object. Shadows are not formed in dark i.e. in absence of light. The shadows are not uniformly dark. Central inner part is darker than outer surrounding part. The darker part of shadow is called umbra and less dark part is called penumbra. There is no change of left part of object to right part of image and right part of object to left part of image.

In nature, solar eclipse and lunar eclipse are examples of shadow formation.

A Pinhole Camera- It is a simple device to indirectly see the bright objects. It works on the principle of straight pathway of light. The sunlight passing through the leaves of a large tree produces numerous circular images of the sun on the ground. It is due to natural pinhole camera formed by the gaps of leaves.

Construction- The requirements for constructing a pinhole camera are- Two rectangular boxes of wood or cardboard, one lager than the other box, butter paper, glue or cello-tape, needle and black colour. The small box was painted black from outside. A rectangular cut was made in the center of one of the side of small box. Over this cut, a piece of butter paper was pasted covering the rectangular hole. The opposite side was used for viewing the image. This smaller box was inserted in a slightly larger box having a tiny hole (pinhole) facing the butter paper of smaller box. This is a pin-hole camera.

Working- The pin-hole camera was used to view a burning candle. An inverted (upside down) image of burning candle was observed on the butter paper. It is based on straight pathway of light.

Precautions- The pinhole made in the lager box should not be wide otherwise clear image of object will not be formed. Do not look the very bright light sources like the Sun for longer time.  

        Mirror- Mirrors are reflective pieces of glass one side of which is silvered.

                     Mirrors can be – Plane mirrors and spherical mirrors

Reflection of Light- The change in direction of light due to any reflective surface like mirror is called refection. The reflected light can be re-reflected by keeping again and again by keeping mirrors the way.

There are two types of reflection of light- i. Regular reflection

                                                                    ii. Irregular or diffused reflection

Activity 1 - Classification of objects into transparent, translucent and opaque.

Requirements- Pencil, Rubber ball, Sheet of writing paper, textbook, plastic ruler, piece of wood, power glasses and torch.

Theory-Light can completely pass through transparent objects, partially pass through translucent objects and do not pass through opaque objects.

Procedure-

Objects	Light passes completely (Transparent)	Light passes partially (Translucent)	Light do not passes (Opaque)
Pencil			Opaque
Rubber ball			Opaque
Writing Paper		Translucent
Textbook			Opaque
Plastic Ruler		Translucent
Clear Water	Transparent
Power Glass	Transparent

Conclusion- On the basis of allowing light to pass or not, the objects are classified into transparent, translucent and opaque.

Activity 2-To demonstrate straight pathway of light

Requirements- Candle, match box, hollow pipe, bended hollow pipe or pipe prepared of paper

Theory- The light travels (or propagates) in a straight line. One can see the light of burning candle by hollow pipe but not by bended pipe.

                                                           

             Figure showing: observations of light through hollow and bended pipes.

Activity 3-Shadow formation by an opaque object

Requirements- A bright source of light like torch, an opaque object like a book or toy, a white cardboard sheet or wall.

Theory- The shadow is dark coloured optical image formed on the screen by an opaque object on opposite side of the source of light. For the formation of a shadow, a source of light, an opaque object and a screen are required. Shadow cannot be seen in dark i.e. in absence of light. Inner part of shadow is comparatively darker than outer fainted part. They are called umbra and penumbra respectively.

Procedure- When torch light falls on the book, the dark coloured shadow of it is formed on the screen like white sheet or wall. Its size is larger or smaller. Note the shape by orienting the rectangular textbook in different directions.

CLASS TEST 1    Time=30 Minutes   Marks= 4 x 5 =20

Q.1 Explain transparent, translucent and opaque objects with a suitable example of each.

Q.2 Differentiate between luminous and non-luminous objects.

Q.3 Prove by an activity that light travels in a straight pathway.

Q.4 What is shadow? What are necessary conditions for formation of a shadow?

CLASS TEST 2    Time=30 Minutes   Marks= 4 x 5 =20

Q.1 What is a pinhole camera? What is it’s use?

Q.2 What is reflection of light? How reflected light can be re-reflected?

Q.3 When our shadow is largest and smallest during the day.

Q.4 Write any three differences between an image and a shadow.

GROUP PROJECTS

1. Prepare a periscope and write its construction and working.

2. Prepare a Kaleidoscope and write its construction and working.

3. Prepare a Pinhole camera and write its construction and working.

SOLVED EXERCISE QUESTIONS

        

Q.1 Rearrange the boxes given below to make a sentence that helps us understand opaque objects.

OWS  AKE  OPAQ  UEO  BJEC  TSM  SHAD

Ans- OPAQ UEO BJEC TSM AKE SHAD OW

Q.2 Classify the objects or materials given below as opaque, transparent or translucent and luminous or non-luminous:

Air, water, a piece of rock, a sheet of aluminium, a mirror, a wooden board, a sheet of polythene, a CD, smoke, a sheet of plane glass, fog, a piece of red hot iron, an umbrella, a lighted fluorescent tube, a wall, a sheet of carbon paper, the flame of a gas burner, a sheet of cardboard, a lighted torch, a sheet of cellophane, a wire mesh, kerosene stove, sun, firefly, moon. 

Ans-

Object	Opaque/transparent/Translucent	Luminous/Non-luminous
Air	Transparent	Non-luminous
Water	Transparent	Non-luminous
A piece of rock	Opaque	Non-luminous
A sheet of aluminium	Opaque	Non-luminous
A mirror	Opaque	Non-luminous
A wooden board	Opaque	Non-luminous
A sheet of polythene	Translucent	Non-luminous
A CD	Opaque	Non-luminous
Smoke	Translucent	Non-luminous
Fog	Translucent	Non-luminous
A piece of red hot iron	Opaque	Luminous
An umbrella	Opaque	Non-luminous
A lighted fluorescent tube	Opaque	Luminous
A wall	Opaque	Non-luminous
A sheet of carbon paper	Opaque	Non-luminous
The flame of a gas burner	Translucent	Luminous
A sheet of cardboard	Opaque	Non-luminous
A lighted torch	Opaque	Luminous
A sheet of cellophane	Translucent	Non-luminous
A wire mesh	Translucent	Non-luminous
Kerosene stove	Opaque	Luminous
Sun	Opaque	Luminous
Firefly	Opaque	Luminous
Moon	Opaque	Non-luminous

Q.3 Can you think of creating a shape that would give a circular shadow if held in one way and a rectangular shadow if held in other way?

Ans- A cylinder will produce a circular as well as rectangular shadow if its position is changed against light. When light falls on it from the top, circular shadow is formed on the screen. But, when light falls on it from the side, rectangular shadow is formed on the screen.                                          

 

 

 

              

Q.4 In a completely dark room, if you hold up a mirror in front of you, will you see a reflection of yourself in the mirror?

Ans- In a dark room I will not be able to see my reflection i.e. image in the mirror. It is because light is essential for formation of an image in the mirror.

 Multiple Choice Questions

1.  In which of the following the speed of light is fastest?

                 (a) Air           (b) Vaccum       (c) Glass           (d) Water

             2. The object which does not emit light is called-

    (a) Opaque object                  (b) Translucent object   

    (c) Luminous object               (d) Non-luminous object

3. Which of the following is a luminous object?

                 (a) The Earth     (b) The Moon     (c) Burning candle    (d) Science Textbook

4. The Moon and all planets of Solar system are –

                 (a) Transparent      (b) Opaque      (c) Luminous       (d) Non-luminous

            5. Which of the following is necessary for formation of shadow?

                (a) A source of light     (b) An opaque object      (c) A Screen     (d) All of these

            6. Which of the following will not form a rectangular shadow?

                (a) A ball     (b) A ruler scale    (c) A circular steel tumbler   (d) An ice-cream cone  

             7. What is essential for formation of a shadow?

                (a) Opaque object         (b) Transparent object      (c) Air      (d) Mirror

             8. Bujhoo and Paheli observed the shadow of a tree at 9:00 A.M., 12:00 P.M. and   3:00 P.M. Which of the following statement is correct about their observation about the shape and size of the shadow of tree?

     (a) The shape changes but size remains same 

     (b)The size changes but the shape remains same   

     (c) Both shape and size change

     (d) Neither shape nor size change

  9.  We see any object because of…………

                  (a) Air                     (b) water                  (c) Light                       (d) Soil

            10. Which is not essential in formation of a shadow?

                   (a) A transparent glass                 (b) An opaque object   

                   (c) A Screen                                     (d) A source of light

            11. Which of the following is a/are luminous object?

                   (a) A glow worm       (b) The Sun       (c) A glowing torch     (d) All of these

              12. What is / are essential for formation of shadow?

                    (a) Screen         (b) Light               (c) Opaque object             (d) All of these

              13. Periscope is based on which principal of light-

                    (a) Refraction of light                            (b) Reflection of light 

                    (c) Diffraction of light                            (d) Interference of light

             14. Beautiful patterns are formed in an optical device because of

                    refection and re-reflection. This device is-                    

           

                    (a)  Periscope     (b) Spectroscope       (c) Kaleidoscope      (d) Telescope

              15. Pin-hole camera has –

                     (a) Very small hole                                   (b) Translucent screen   

                     (c) Opening for eyes                                 (d) All of these

                             VERY SHORT ANSWER TYPE QUESTIONS

              1. Give two examples each of natural and artificial sources of light.

              2. Give two examples each of luminous and non-luminous objects.

              3. What is the use of pinhole camera?

              4. What is shadow?

              5. What is the colour of shadow?

 

                SHORT ANSWER TYPE QUESTIONS

               1. Define luminous and non-luminous objects.

               2. When shadow of a tree is larger and smaller than the tree?

               3. What is mirror? Write the two characteristics of images formed by a mirror?

               4. Why the direction of light changes when light falls on plane mirror?

               5. The leaves of crown of a tree form numerous circular patches on ground. Why?

                LONG ANSWER TYPE QUESTIONS

       1. What is shadow? What are necessary conditions for formation of a shadow?

       2. Explain the working of Pinhole camera with a simple diagram of it.

       3. Sort out the objects given below into-

                          (a) Natural sources and artificial sources of light

                          (b) Luminous and Non-luminous objects

          The Earth, Apple, Glowing bulb, The Sun, School bag, Book, Football, Torch,   Fireflies, Lighter, Mobile Phone, Ink Pen, and Crayons

 

PISA TYPE/ HOTS TYPE QUESTIONS-    Time = 15 minutes   Total marks =1 x 5=5

 

 

                           Fig.1                                                             Fig.2

Look at the two above figures. They are reflections from the reflective surfaces. Black coloured rays show the incident rays while the blue coloured rays show the reflected rays. The reflection of light on the plane (or smooth or regular or even) reflective surface follows the laws of reflection of light but this law fails on the diffused (or irregular surface or rough or uneven) surface. Based on this, answer the following questions-

(a) Figure 1 shows which type of reflection of light?

(b) Figure 1 shows which type of reflection of light?

(c) In which figure the laws of reflection of light fail?

(d) In which figure the laws of reflection of light are followed?

(e) In nature generally which refection of light from objects can be correlated with which figure?