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GURUKUL CENTRAL ACADMY, CH.- 16 - light, WORKSHEET-1 & 2, Refer Text book, , TEXTBOOK EXERCISES, Page 180 Try These, 1. Irregular surface 2. Regular reflection, 3. Kaleidoscope, periscope, 4. Infinitive, Page 182 Try These, 1. periscope, 2. dispersion of light, , 3. myopia 4. 25 cm, , EXERCISES, A. 1. b. 2. a. 3. a. 4. a. 5. a. 6. c. 7. b. 8. d. 9. d. 10. c., B. 1. F 2. T 3. T 4. F 5. F 6. T 7. F 8. F 9. F, C. 1. reflection, 2. point of incidence 3. in dimlight, 4. contracts5. Optic nerve 6. Auditory aid, 7. Olfactory aid 8. multiple images 9. Kaleidoscope, D. 1. – b. 2. – d. 3. – e. 4. – c. 5. – a.

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GURUKUL CENTRAL ACADMY, E. 1., , The phenomenon in which the left side of an object appears right, and the right side of the object appears left is known as lateral, inversion., , 2., , At the junction of the retina and optic nerve, is present a nonsensory area. This is known as blind spot., , 3., , The phenomenon in which the image of an object remains in front of, our eyes for 1/16th of a second is called persistence of vision., , 4., , The phenomenon of splitting sunlight or white light into seven, colours is called dispersion of light., Regular Reflection: When reflection of light takes place from a, smooth plane surface in which the reflected rays are parallel to one, another, it is known as regular reflection., Diffused Reflection: When the reflection of light takes place from, a rough surface in which the reflected rays are not parallel to each, other, it is known as diffused reflection., , F. 1., , 2., , Myopia:, 1. When the eyes cannot focus on far off objects but can focus on, nearby objects clearly, the defect is referred to as myopia., 2. It is corrected by using glasses with concave lens., Hypermetropia:, 1. When the eyes cannot focus on nearby objects but can focus on, far off objects clearly, the defect is referred as hypermetropia., 2. It is corrected by using glasses with convex lens.

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GURUKUL CENTRAL ACADMY, 3., , Reflection of light:, The bouncing back of light from a surface is called reflection of, light., Refraction of light:, The phenomenon of bending of light when it travels from one, medium to another is called refraction of light., , G. 1., , The ray of light which strikes the mirror is called incident ray., Imaginary line which is perpendicular to the point at which the, incident ray strikes is called normal ray., The ray of light which reflects back after the incident ray strikes the, mirror is called reflected ray., , 2. When a part of light falling on an object bounces back and, reaches our eyes, it makes an image of the object in our eyes. And, thus we are able to see it., 3. 5, 4., , Our eyes also have a wonderful ability to focus and see nearby as, well as far off objects clearly by changing the thickness of the lens., This property is called accommodation power of eyes. The least, distance of distinct vision is 25 cm., , 5., , The eye lens becomes foggy due to regular wear and tear for so, many years. If this continues a new ailment arises which is known, as cataract., , 6., , Angle of incident = 45o Angle of reflection =, 45o

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GURUKUL CENTRAL ACADMY, 7., , Myopia and hypermetropia. They can be cured by using, respectively concave and covex lens., , 8., , Whenever light coming from an object suffers more than one, reflection, it leads to the formation of multiple images., , 9., , An optical instrument used to see multiple images is called, kaleidoscope., , 10., , The image formed by a plane mirror is:, • erect and of the same size as the object., • at the same distance behind the mirror as the object is in front of, the mirror., , 11., , When two mirrors are kept together with one of their edges, joining, then the angle between the mirrors determines the number, of images formed by it. In this case light ray from an object after, striking the mirror gets reflected. This reflected light again strikes, the mirror and reflects back, producing multiple images of the, object., , H. 1., , First Law of Reflection: The incident ray, the normal at the point, of incidence and the reflected ray – all lie in the same plane. It, means AO, ON and OB are in the same plane., Second Law of Reflection: The angle of incidence is always equal, to the angle of reflection., , Refer fig. 16.3.

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GURUKUL CENTRAL ACADMY, 2., , Cornea:, It is the transparent front part of the eye that covers the iris, pupil, and the anterior part of the eye., Iris:, It is a thin circular structure present in the eye in which pupil is, located. It gives colour to our eyes., Pupil:, It is a hole located in the centre of the iris that allows the light to, enter the eyes., Eye lens:, It is a transparent biconvex lens in the eye that helps to refract light, so that it can be focused on the retina., Retina:, It is a light sensitive tissue in the eye on which the focused light, forms the image of the object. It acts like a screen. The sensation of, the image formed on the retina is sent to the brain through a nerve, called optic nerve. A highly light sensitive spot is at the centre of, the retina where image of an object is focussed. It is called yellow, spot., , Refer fig. 16.19., 3., , Our eyes are one of the most essential organs of our body. Most of, us take them for granted and don’t pay much attention to their, health. We only realize their importance if some kind of ailment, develops. Thus, it is very essential to take good care of our eyes., We can take care of them in the following manner:, • Take a vitamin A rich diet such as papaya, eggs, fish, milk, green, vegetables and fresh fruits to make the eyes healthier. Deficiency, of vitamin A causes nightblindness which makes it difficult to see, in dim light or at night. Wash the eyes with cold water to remove, dust and dirt., • If any unwanted dust particles go into your eyes, it is advisable

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GURUKUL CENTRAL ACADMY, •, , •, , not to rub the eyes to remove them., Don’t overstrain your eyes by reading in dim light. Moreover,, text shouldn’t be very far or very close to our eyes when we are, reading., Splash cold water two to three times to wash your eyes., , 4., , If our eyes look at an object, the sensation of it remains in front of, our eyes for 1/16th of a second. This phenomenon is called, persistence of vision. Animation works on the phenomena of, persistence of vision. Illustrations are made on pages which are, called frames. Each frame is flashed on the screen for a very short, period of time and replaced by a next sequence of frames. Due to, persistence of vision, our eyes create an optical illusion which, seems as if the object is in motion., , 5., , Refer page 180.