This textbook was compiled by the Educational Publications Department inaccordance with the syllabus prepared by the National Institute of Education forthe use of Grade six students in the Sri Lankan school system with effect from 2015.An effort has made here to arrange the subject content to suit the national educationalgoals, common national competencies, the objectives of teaching science and thecontent of the syllabus.The subject of science directs the student towards a more active learning process ina manner as to develop knowledge, skills and attitudes needed for a developmentalscientific thought.In the compilation of this textbook, subject content is largely arranged based onexperiences of daily life. It has contributed to prove the fact that the subject ofscience is very much closer to the day to day life.The compilation of this textbook based on activities is a distinctive feature. Theactivities are prepared based on the scientific method in order to develop knowledge,skills and attitudes. Activities that can be performed individually at home as well asin school are incorporated here. We believe that learning through activities wouldcontribute to create a liking and an interest in the child towards learning science.At the end of each chapter, a summary, a series of exercises and a glossary wereincluded. It enables the student to identify the important details of the chapter aswell as to self evaluate the achievement of learning outcomes.For the purpose of directing the student to study further about the subject matter,more information is included in the \'For your extra Knowledge\'. It is given only tobroaden the subject area of the child and certainly not to ask questions at term tests.Assignments and projects are given with the purpose of directing the studenttowards an explorative study. It enables the students to develop the higher orderskills such as application, analysis and synthesis of the concepts achieved from thelesson.We strongly believe that the duty of the teachers who teach science is to direct thestudent for self learning instead of teaching the student using traditional teachingmethods. This textbook can be utilized by the teachers as a learning tool to executetheir teaching role properly.We would like to bestow our sincere thanks on the Senior Lecturer Asoka De Silvaand the Chief Project Officer (Retired) W.D.Wijesinghe of the National Institute ofEducation and the Retired Principal H.S.K. Wijethilake.We kindly request you to forward your comments and suggestions on this textbookto the Educational Publications Department.
For entertainment In musical shows and fairs, light is used in a large scale. They use spot lights of different colours to light up the stage. Even lights are used, in toys designed for children. Fig. 5.13 Light emitting toys To produce light artifically we have to spend money. Therefore, unnecessary usage of light is a wastage of energy and money. So, we must always be cautious enough to stop the wastage of light and at the same time we must use it without making a disturbance to others. 82 Do you know? When there is a lot of fog, it is very difficult to travel on roads as we can't see anything. But light beams of headlights could be seen through fog. The reason is that air is transparent on normal foggy conditions but air becomes translucent on foggy conditions. When the humidy is high in air, air becomes translucent. There is a new type of lamp in modern vehicles as fog light to be used when the atmosphere becomes translucent because of the mist.
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Optical fibers are a type of flexible fibers which are made up of special type of glass or plastic. An optic tube is called a collection of such fibers. The use of such tubes to transport light is called optic fiber technology. The first bulb with carbon filaments in the United States of America was invented by Thomas Alva Edison in 1879. 83 Summary The main factors that must be satisfied to have complete vision are light and the eye. The objects we use to get light are known as sources of light. Objects which emit their own light are known as luminous objects while the ones which cannot emit light are known as non luminous objects. The way light transmits through objects differs from object to object. According to that, we categorize them as transparent, translucent and opaque. Light transmits in straight lines. The combination of light rays is called a light beam. There are many applications of light, apart from giving vision.
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Exercise 01.Select the correct answer. i. Choose the correct statement. a.The moon is a luminous object. b.The sun is a source of light. c. Planets are non luminous objects. i. Only a and b ii. Only b and c iii. All are correct iv. All are wrong ii. The correct statement of the followings is, a. Water, glass and decorative glass are transparent. 84 b. Water, polythene and oil papers are translucent. c. Oil papers, decorative glass and colourless polythene are transparent. d. Cardboards, metal and papers are opaque. iii. Why can we see a light ray travelling through the roof of a kitchen which is filled with smoke? a. Because the kitchen becomes translucent when filled with smoke. b. Because the kitchen becomes transparent when filled with smoke. c. Because light transmits through air.
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Because smoke absorbs light. 02. Fill in the blanks with the correct word. Light is a type of '''''''''''''''''''''''''''''''' It travels in a '''''''''''''''''''''''''' '''''''''''''''''''''''''' Light does not travel through some objects. Such objects are known as......................... To indicate the direction in which light transmits, ........................... is used.In most of the road signals,........................... is used to gain more attention. light) 02. Fill in the blanks with the correct word. Light is a type of '''''''''''''''''''''''''''''''' It travels in a '''''''''''''''''''''''''' '''''''''''''''''''''''''' Light does not travel through some objects. Such objects are known as......................... To indicate the direction in which light transmits, ........................... is used.In most of the road signals,........................... is used to gain more attention. light)
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