Science

13.9 Visually Impaired dust go into your eyes, wash your eyes with clean water. If there is no Persons Can Read and

13. 9 Visually Impaired dust go into your eyes, wash your eyes with clean water. If there is no Persons Can Read and improvement go to a doctor. Write - Always read at the normal distance Some persons, including children, can for vision. Do not read by bringing be visually impaired. They have very the book too close to your eyes or keeping it too far. limited vision to see things. Some persons cannot see at all since birth. You learnt about balanced diet in Some persons may lose their eyesight Class VI. If food is deficient in some because of a disease or an injury. Such components, eyes may also suffer. Lack of vitamin A in foodstuff is responsible persons try to identify things by for many eye troubles. Most common touching and listening to voices more amongst them is night blindness. carefully. They develop their other One should, therefore, include in the senses more sharply. However, diet components which have vitamin A. additional resources can enable them Raw carrots, broccoli and green to develop their capabilities further. 2024-25 Non-optical and optical aids for visually impaired Non-optical aids include visual aids, tactual aids (using the sense of touch), auditory aids (using the sense of hearing) and electronic aids. Visual aids, can magnify words, can provide suitable intensity of light and material at proper distances. Tactual aids, including Braille writer slate and stylus, help the visually challenged persons in taking notes, reading and writing. Auditory aids include cassettes, tape recorders, talking books and other such devices. Electronic aids, such as talking calculators and computers, are also available for performing many computational tasks. Closed circuit television, also an electronic aid, enlarges printed material with suitable contrast and illumination. Nowadays, use of audio CDs and voice boxes with computers are also very helpful for listening to and writing the desired text. Optical aids include bifocal lenses, contact lenses, tinted lenses, magnifiers and telescopic aids. While the lens combinations are used to rectify visual limitations, telescopic aids are available to view chalkboard and class demonstrations. 13. 10 What is the Braille Braille system has 63 dot patterns or System? characters. Each character represents a letter, a combination of The most popular resource for visually letters, a common word or a challenged persons is Braille. grammatical sign. Dots are arranged in cells of two vertical rows of three Louis Braille, himself a visually dots each. challenged person, developed a Patterns of dots to represent some system for visually challenged persons English letters and some common and published it in 1821. words are shown below. Louis Braille Example of dot patterns used in Braille System The present system was adopted in These patterns when embossed on 1932. There is Braille code for common Braille sheets help visually languages, mathematics and scientific challenged persons to recognise words notation. Many Indian languages can by touching. To make them easier to be read using the Braille system. touch, the dots are raised slightly. 2024-25 Visually impaired people learn the character has to be memorised. Braille Braille system by beginning with texts can be produced by hand or by letters, then special characters and machine. Typewriter-like devices and letter combinations. Methods depend printing machines have now been upon recognition by touching. Each developed. Some visually impaired Indians have great achievements to their credit. Diwakar, a child prodigy has given amazing performances as a singer. Ravindra Jain, born completely visually impaired, obtained his Sangeet Prabhakar degree from Allahabad. He had shown his excellence as a lyricist, singer and music composer. Lal Advani, himself visually impaired, established an Helen A. Keller Association for special education and rehabilitation of disabled in India. Besides this, he represented India on Braille problems in UNESCO. Helen A. Keller, an American author and lecturer, is perhaps the most well- known and inspiring visually challenged person. She lost her sight when she was only 18 months old. But because of her resolve and courage she could complete her graduation from a university. She wrote a number of books including The Story of my Life (1903). 2024-25 KKEEYYWWOORRDDSS WWHHAATT YYOOUU HHAAVVEE LLEEAARRNNTT ANGLE OF (cid: 220) Light is reflected from all surfaces. INCIDENCE (cid: 220) Regular reflection takes place when light is ANGLE OF incident on smooth, polished and regular REFLECTION surfaces. (cid: 220) Diffused or irregular reflection takes place from BLIND SPOT rough surfaces. BRAILLE (cid: 220) Two laws of reflection are CONES (i) The angle of incidence is equal to the angle CORNEA of reflection. - Incident ray, reflected ray and the normal DIFFUSED OR drawn at the point of incidence to the IRREGULAR reflecting surface, lie in the same plane. REFLECTION (cid: 220) Image formed in a plane mirror undergoes INCIDENT RAYS lateral inversion. IRIS (cid: 220) Two mirrors inclined to each other give multiple KALEIDOSCOPE images. (cid: 220) Beautiful patterns are formed in a LATERAL INVERSION kaleidoscope because of multiple reflections. LAWS OF (cid: 220) Sunlight, called white light, consists of seven REFLECTION colours. PUPIL (cid: 220) Splitting of light into its constituent colours is REFLECTED RAYS known as dispersion. (cid: 220) Parts of the eye are cornea, iris, pupil, lens, REFLECTION retina and optic nerve. REGULAR (cid: 220) A normal eye can see nearby and distant REFLECTION objects clearly. RETINA (cid: 220) Visually impaired persons can read and write RODS using the Braille system. (cid: 220) Visually impaired persons develop their other senses more sharply to improve their interac- tion with their environment. 2024-25


Science

[Exercise] ## Exercises 1. Suppose you are in a dark room. Can you see objects in the room? Can you see objects outside the room. Explain. 2. Differentiate between regular and diffused reflection. Does diffused reflection mean the failure of the laws of reflection? 3. Mention against each of the following whether regular or diffused reflection will take place when a beam of light strikes. Justify your answer in each case. (a) Polished wooden table (b) Chalk powder - Cardboard surface (d) Marble floor with water spread over it (e) Mirror (f) Piece of paper 4. State the laws of reflection. 5. Describe an activity to show that the incident ray, the reflected ray and the normal at the point of incidence lie in the same plane. 6. Fill in the blanks in the following. (a) A person 1 m in front of a plane mirror seems to be __ m away from his image. (b) If you touch your __ ear with right hand in front of a plane mirror it will be seen in the mirror that your right ear is touched with __. - The size of the pupil becomes __ when you see in dim light. - Night birds have __ cones than rods in their eyes. Choose the correct option in Questions 7 - 8 7. Angle of incidence is equal to the angle of reflection. (a) Always (b) Sometimes - Under special conditions (d) Never 8. Image formed by a plane mirror is (a) virtual, behind the mirror and enlarged. (b) virtual, behind the mirror and of the same size as the object. - real at the surface of the mirror and enlarged. - real, behind the mirror and of the same size as the object. 9. Describe the construction of a kaleidoscope. 10. Draw a labelled sketch of the human eye. 2024-25 11. Gurmit wanted to perform ## Activity 13. 8 using a laser torch. Her teacher advised her not to do so. Can you explain the basis of the teacher's advise? 12. Explain how you can take care of your eyes. 13. What is the angle of incidence of a ray if the reflected ray is at an angle of 90° to the incident ray? 14. How many images of a candle will be formed if it is placed between two parallel plane mirrors separated by 40 cm? 15. Two mirrors meet at right angles. A ray of light is incident on one at an angle of 30° as shown in Fig. 13. 19. Draw the reflected ray from the second mirror. Fig. 13. 19 16. Boojho stands at A just on the side of a plane mirror as shown in Fig. 13. 20. Can he see himself in the mirror? Also can he see the image of objects situated at P, Q and R? Fig. 13. 20 17. (a) Find out the position of the image of an object situated at A in the plane mirror (Fig. 13. 21). (b) Can Paheli at B see this image? - Can Boojho at C see this image? - When Paheli moves from B to C, where does the image of A move? Fig. 13. 21 S E S I C R E X E 2024-25 Extended Learning - ## Activities and Project 1. Make your own mirror. Take a glass strip or glass slab. Clean it and put it on a white sheet of paper. See yourself in the glass. Next put the glass slab on a black sheet of paper. Again look into the glass. In which case do you see yourself better and why? 2. Make friends with some visually impaired students. Enquire from them how they read and write. Also find out how they are able to recognise objects, hurdles and currency notes. 3. Meet an eye specialist. Get your eye sight checked and discuss how to take care of your eyes. 4. Survey your neighbourhood. Find out how many children below the age of 12 years use spectacles. Find out from their parents what, in their view, could be the reason for the weak eyesight of their children. Did You Know? Eyes can be donated by any person as an invaluable gift to visually impaired persons suffering from corneal blindness, The person may be (a) a male or female. (b) of any age. - of any social status. - using spectacles. (e) suffering from any normal disease but not AIDS, Hepatitis B or C, rabies, leukemia, lymphoma, tetanus, cholera, encephalitis. The eyes have to be donated within 4-6 hours after death at any place, home or hospital. A person who wants to donate the eyes may pledge eyes during his/her lifetime to any registered eye bank. He/she should also inform his/her relatives about this pledge so that they can take necessary action after his/her death. You can also donate a Braille kit. 2024-25 Notes 2024-25 Notes 2024-25


Science

a few times to interact with one another to improve the draft. Then there was a review meeting in which many experts and practicing school teachers were invited to review the draft and suggest improvements. By and large we have stuck to the format of the Class VII book. By now famous characters, Boojho and Paheli, have been used to make the text interactive. Attempt has been made to recall children's own experiences and build concepts around them. This is designed to connect science that they study in the school with their everyday life. Many activities have been suggested to clarify concepts. Some of these activities are so simple that children can perform them on their own. The requirement of the apparatus required for the activities is minimal. We performed all the activities ourselves to ensure that there was no difficulty in performing them in the school situation. The activities should also help children in developing skills such as presentation of data in tabular and graphical forms, reasoning and drawing inference from the given data. The language of the book has been kept as simple as possible. A large number of photographs, illustrations, cartoons, etc. have been included to make the book attractive. To help teachers evaluate children effectively, a large number of exercises have been given at the end of each chapter. The teachers are encouraged to frame additional exercises to test children's understanding. Some challenging exercises have also been devised for those children who would like to appear for the National Talent Search Examination conducted by the