Page 1 : OPTICS, , Science, Light is a form of energy that makes us to see., An object reflects the light that falls on it. This, reflected light, when received by our eyes,, enables us to see. We are able to see through a, transparent medium as light is transmitted, through it. The speed of light in vacuum or in air, is 3 × 108 m/s, It is the branch of science in which we study, about light and its properties, nature etc. Optics, is classified into two types; ray optics and wave, optics, Ray Optics, It deals with light rays linear propagation of light, such as reflection, refraction, dispersion etc., Wave Optics, It deals with wave nature of light such as, polarization, diffraction etc., Properties of Light, (i) Light travels in a straight line., (ii) A straight line drawn in the direction of, propagation of light is called a ray of light., (iii) A bundle of adjacent light rays is called, beam of light., (iv) The speed of light in vacuum is 3 × 108 m/s, but it is different in different media., (v) The speed and wavelength of light, changes when it travels from one medium, to another but its frequency remains, unchanged., , Class Notes, (ii), , Angle of incidence is always equal to the, angle of reflection.,  Silver metal is one of the best, reflectors of light.,  Laws of reflection apply to all kinds of, reflecting surface., , Mirror:Mirror is a polished surface like glass, which, reflects almost all the light that is incident on it., Types of Mirror, There are two types of mirror, 1. Plane Mirror, If the reflecting surface of a mirror is plane, then, the mirror is called a plane mirror. Image formed, by a plane mirror has following properties, i. It is always virtual and erect., ii. The size of image is equal to the size of the, object., iii. The image formed is far behind the mirror as, the object is infront of it., Iv Linear magnification produced by place mirror, is 1., v. The minimum size of the mirror required to, see the full image of an observer is half the, height of the observer. If the plane mirror is, rotated in the plane of incidence by an angle, 𝜃, then the reflected ray rotates by angle 2𝜃, vi. Focal length of a plane mirror is infinity (i.g.,, power is zero)., vii. If the object is displaced by a distance ‘𝛼’, towards or away from the mirror, then its, image will be displaced by a distance ‘𝛼’, towards or away form the mirror., , The sun, stars and other astronomical bodies in, the universe are the natural source of light. There 2. Spherical Mirror, are some artificial sources of light like electric A highly polished curved surface whose, bulbs. Candles etc., reflecting surface is a cut part of a hollow glass, sphere is called a spherical mirror., Reflection of Light, i. Concave Mirror:- The spherical mirror whose, The phenomenon of rebouncing back of light reflecting surface is inwards and outer surface is, rays in same medium on striking a smooth polished is called concave mirror., surface, is called reflection of light., It is also called converging mirror because, it is, The laws of reflection are, generally used to converge the beam of light after, (i) The incident ray, the reflected ray and reflection., the normal to the reflecting surface at, the point of incidence all lie in the same, plane.

Page 2 : Here, F= focal length, R= radius of curvature., ii. Convex Mirror:- A spherical mirror whose, outer surface is reflecting the inner surface is, Image, polished is called convex mirror. It is also called, If light rays coming from a point after reflection, diverging mirror because it generally diverges, meet at another point or appear to come from, beam of light after reflection., another point, then the second point is called the, image of the first point., Important terms related to spherical Types of Image, mirror, There two types of image, i. Centre of Curvature (C):- The centre of the i. Real Image:- If the light rays coming from a, sphere of which the mirror is a part, is called, point actually, meet after reflection. Then the, the centre of curvature of the mirror., image formed is called a real image., ii. Radius of Curvature (R):- The radius of the ii. Virtual Image:- If the light rays coming from a, sphere of which the mirror is a part is called, point, after reflection does not meet actually,, the radius of curvature of the mirror., but appear to come from another point, then, iii. Principal Axis:- The straight line joining the, the image formed is called a virtual image., pole and the centre of curvature of the mirror,  If half of the mirror is covered, the image, and extended on both sides is called the, formed is complete but is intensity reduces, principal axis of the mirror., (because less amount of light is reflected, iv. Pole (p):- The central point of the reflecting, from the mirror)., surface of the mirror is called the pole of the,  The origin of multiple images is the multiple, mirror., reflection of light between the front and back, v. Aperture:-The diameter of the reflecting, surfaces of glass. At the front surface of, surface of spherical mirror is called its, glass, light is partially reflected and partially, aperture., reflected and partially refracted. The, vi. Focal Plane:- The plane perpendicular to the, refracted light gets reflected at the back, principal axis and passing through the, surface and then multiple reflections follow, principal focus of the mirror is called the focal, within the thickness of glass, which is, plane of the mirror., responsible for multiple images., vii. Focal Length (f):- The distance between the, principal focus and pole of the mirror is called Image Formation by spherical Mirror, the focal length of the mirror. If the aperture Image formation by a concave and a convex, 𝑅, mirror is shown separately., of mirror is small then, 𝑓 − ., 2, , viii. Principal Focus(F):- The point of the, principal axis at which light rays parallel to the, principal axis, after reflection from the mirror,, actually meet or appear to come from, is, called the principal focus of the mirror., , Image Formation By a Concave Mirror, The table given below illustrates the ray, diagrams along with the position and nature of, image, formed b concave mirror for various, positions of the object., Position of, the object, , M1, Principal axis, , Focus, , Ray Diagram, , Position, of, the image, , Nature of the, image

Page 3 : At infinity, , At focus or in, the, focal, plane., , Real,, Inverted, extremely, diminished in, size, , , , They are used to make kaleidoscope, a toy, which produces beautiful patterns from, coloured paper, pieces of glass or small, coloured beads., Beyond the, Between, Real,, ii. Uses of Concave Mirrors, Centre, of, focus and the Inverted,  Concave mirrors are commonly used in, curvature, centre, of diminished, but at finite, curvature, torches, search lights and vehicles headlights, distance, to get powerful parallel beams of light., At the centre, At the centre Real,,  Concave mirrors are used as shaving mirrors, of curvature, of curvature, Inverted and, to see larger image of the face., equal to the, object,  Dentists used concave mirrors to see large, Between, Beyond, the Real,, images of the teeth., focus, and, centre, of Inverted and, , Large concave mirrors are used to, centre, of, curvature, bigger than, concentrate sunlight to produce heat in solar, curvature, object, furnaces., At the focus, At infinity, Real,, Inverted, iii. Uses of Convex Mirrors, extremely,  Convex mirrors are commonly used as rear, diminished, Between the, Behind, the Erect ,virtual, view mirrors in vehicles because they always, pole, and, mirror, and, give an erect image and have wider field of, focus, magnified, view as they are curved outwards.,  Big convex mirrors are used as shop security, mirrors; the shop owner can keep an eye on, Image Formation by convex mirror, the customers to look for thieves and, For studying the image formed by mirror, there, shoplifters among them., are two positions of the object. Firstly, when the, , object is at infinity and the second position is, when the object is at a finite distance from the, mirror. The table given below illustrates the ray, diagrams along with the position and nature of, image, formed by convex mirror for the above, two positions of the object., Position, Object, , of, , Ray diagram, , Position, image, , of, , At Infinity, , At the principal, focus, , Between, infinity and the, pole (i.g., at, finite distance), , Between the, principal focus, and the pole, , Refraction of Light, Change in path of a light ray as it passes from one, medium to another is called refraction. When light, travels from a rarer medium to a denser one, it bends, towards the normal (i< r) and when travels from, denser medium to a rarer one, it bends away from the, normal (i>r)., , Nature and, size, of, image, Virtual,, erect, and, extremely, diminished, , (i>r), , (i<r), , Virtual,, erect, and, diminished, , Uses of Mirrors, Uses of mirrors can be explained in different ways, i. Uses of Plane Mirrors,  Plane mirrors are commonly used as looking, glass because the reflection that forms the, image is always erect latterly inverted but they, are always virtual.,  Used in making periscopes which is used in, submarines.,  Used at blind turns of some busy roads, to see, the vehicles coming from other side., , Here, i= angle of incidence r= angle of refraction,  A medium in which the speed of light is more, is known as optically rarer medium and the, medium in which speed of light is lesser is, known as optically denser medium., Cause of Refraction, Speed of light is different in different media. It is lesser, in denser medium and greater in rarer medium. So,, when light enters a denser medium, its speed, reduces and it bends towards the normal and when it, enters rarer medium, its speed increases and it bends, away from the normal., , Refractive Index

Page 4 : The ratio of speed of light in vacuum to the speed of, light in any medium, is called refractive index of the, medium., The refractive index of a medium relative to another, medium, is known as the relative refractive index of, given pair of media., Laws, of, Refraction, (Snell’s, Law), There are two laws of refraction, i. The incident ray, the refracted ray and the normal, at the point of incidence all three lie in the same, plane., ii. The ration of sine of angle of incidence to the sine, of angle of refraction remains constant of a pair of, media., 𝑠𝑖𝑛𝑖, 𝑠𝑖𝑛𝑟, , = constant (1𝜇2), , atmosphere, it undergoes atmospheric refraction and, bends towards the normal at position each time., The upper layers of atmosphere are rarer than the, lower layers. The apparent position of the star is, slightly different from its actual position. The star, appears slightly higher (above) than its actual, position, when viewed near the horizon., Scattering of Light, The reflection of light from an comparably smaller, sized particle in all directions, is called scattering of, light. The colour of scattered light depends on the size, of scattering particles. Very fine particles scatter, mainly blue light while particles of larger size scatter, light of longer wavelength (red light). If the size of the, scattering particles is large enough then the scattered, light may even appear white. The blue present in, sunlight is scattered 10 times more than the red light., , =, There law is also called Snell’s law. The constant 1𝜇2 Why is the Colour of the Sky blue? During the day, time sky appears blue. This is because the size of the, is known as relative refractive index., particles in the atmosphere is smaller than the, wavelengths (blue end of spectrum)., Critical Angle, The angle of incidence in a denser medium for which When sunlight passes though the atmosphere, the, the angle of refraction in rarer medium becomes 90o, fine particles scatter the blue colour more strongly, is called critical angle (C). The value of critical angle than red. The scattered blue light enters our eye., depends on the nature of two media and colour of Hence, the sky appears blue. It should be noted that, the sky appears black to the passengers flying at, light., Refractive index of denser medium (when rarer higher altitudes because scattering of light is not, prominent at such height due to the absence of, medium is air), particles., 1, Colour of the Sun at Sunrise and Sunset:- At, 𝜇=, 𝑠𝑖𝑛𝐶, sunrise and sunset, the Sun and they sky appears, red. Light from the Sun near the horizon passes, through thicker layers of air and covers larger, Atmospheric Refraction, The Earth’s atmosphere is not uniform throughout, its distance in the atmosphere before reaching our eyes., density goes on changing as we move up or down. It Near the horizon most of the blue light and shorter, can be considered to be consisted of layers of wavelengths are scattered away by the particles., different densities, which acts as rarer or denser Therefore, the light that reaches our eyes is of longer, medium with respect to one other. The refraction of wavelengths. This gives rise to the reddish, light due to these layers, is called atmospheric appearance., refractions., Some Phenomena, Refraction, , Based, , on, , Atmospheric, , Twinkling of Stars:- The twinkling of a star is due to, atmospheric refraction of starlight. As the light from, the star enters the Earth’s atmosphere, it undergoes, refraction due to varying optical densities of air at, various altitudes. The continuously changing, atmosphere refracts the light by different amounts. In, this way, the starlight reaching our eyes increases, and decreases continuously and the star appears to, twinkle at night., However at the noon, the light from the Sun overhead, The Stars Seem Higher than They Actually would travel relatively shorter distance. So, it appears, Appear:- As the light from a star enters the Earth’s

Page 5 : white as only a little of the blue and violet colour are, scattered., Total Internal Reflection (TIR), When a light ray, travelling from a denser medium, towards a rarer medium is incident at the interface at, an angle of incidence greater than critical angle, then, light rays are reflected back into the denser medium, (i.g., same medium). This phenomenon is called total, internal reflection., Necessary conditions for total internal reflection to, take place are, i. The ray incident on the interface of two media, should travel from denser medium to rarer medium., ii. The angle of incident should be greater than critical, angle for the two media., , observer, inverted image of tree is obtained which, produces illusion of water., , Cool air, , Hot air, , 3. Diamond, Practical Applications of Total Internal Reflection, Brilliance of diamond is mainly due to total internal, 1. Optical Fibre, reflection of light inside them. The critical angle for, The working of optical fibre is based on total, diamond air interface is very small, therefore once, internal reflection. Its inner part is core of, light enters the diamond, it is very likely to, higher reflective index surrounded by another, undergo total internal reflection. Brilliance of, layer of glass of lower refractive index. It is, diamond depends on tis cutting. By cutting the, surrounded by a plastic jacket., diamond suitably, multiple total internal reflections, When light enters from the one end of the core, can be made to occur., and moves towards cladding, then total, internal reflection takes place again and, again, and light propagates through it. Optical Colour of Object, fibres are used in decorative table lamps., When light is incident on an object, it reflects only a, part of it. The reflected light gives the objects with, Uses of Optical Fibre, their colours., i. These are used to send an electrical, signal by transforming it into a light signal Colours, and vice-versa., Colours can categorised into following three, ii. These are used to send laser light rays categories, inside the human body., iii. Today optical fibres are frequently used in Primary colours:- primary colours are sets of colours, telecommunication., that can be combined to make a useful range of, iv. These are used in decorative table lamps. colours. e.g., red, green and blue are primary colours., v. These are used in networking, because, each fibre an can carry many signals, Secondary colours:- The colours which are, each using a different wavelength of light. obtained by the mixing of two primary colours, are, called secondary colours., 2. Mirage, e.g., yellow, magenta and cyan are secondary, Mirage is the optical illusion of water appears in colours., desert in a hot summer day. In a hot summer day, in desert, the layers of air near the earth surface, Red+ Green= Yellow, remains hot and their temperature decreases with, Red+ Blue= Magenta, altitude and become denser. When a ray of light, Green+ Blue= Cyan, coming from the top of a tree or sky, moves, towards the earth and deviates away from the, normal gradually. When angle of incidence, becomes greater than critical angle, total internal, reflection takes place. After that light rays bend, upward. When, light rays enter the eyes of an

Page 6 : Complementary Colours:- Those primary and, secondary colours which on mixing produce white, colour, are called complementary colours., e.g.,, Red + Cyan = White, Green + Magenta = White, Blue + Yellow = White, Refraction by Spherical Lenses, Lens is a transparent medium bounded by two, surface of which, one or both surfaces are spherical., Lenses are of two types, , Formation of Image by a Convex Lenses, The table given below illustrates the ray diagrams, along with the position and nature of image, formed, by convex lens for various positions of the object., Formation if Image by Convex Lens for Different, Positions of Objects, Image formation by Convex Lens, Object, , Image, , Image, , Image, , location, , locatio, , size, , nature, , Diminis, , Real and, , hed, , Inverted, , n, At Infinity, , 1. Convex or converging lens, A lens which is thicker at the centre and thinner at its, end, is called convex lens., , Ray Diagram, , At F2, , Beyond 2, , Betwee, , Small, , Real and, , F1, , n 2F2, , size, , Inverted, , Small, , Real and, , size, , Inverted, , Beyon, , Magnifi, , Real and, , d 2F2, , ed, , Inverted, , At, , Highly, , Real and, , infinity, , Magnifi, , Inverted, , and F2, Between, , At 2F2, , 2F1 and, F1, At 2 F1, , (a)Double convex lens (b) Plano-convex lens (C) Convex lens, , , , , , A convex lens is also known as converging, lens because it converges a parallel beam of, light rays passing through it, A double convex lens is simply called convex, lens., , At F1, , ed, Between, , On the, , Magnifi, , lens and, , same side ed, , F1, , as the, , Virtual, and Erect, , 2. Concaveor Diverging lens, object, A lens which is thinner at the centre and thicker at its, end, is called a concave lens. Concave lenses are of, Formation of Image by a Concave Lens, three types (as shown), The table given below illustrates the diagram along, with the position and nature of image, formed by, concave lens for the above two positions of the, object., Formation of image by Concave Lens for Different, Positions of Object, Formation of Image by Concave Lens for Different, Positions of Object, , (a)Double concave lens, , , , (b) Pleno-conceve lens, , (c)Convexo-concave lens, , A concave lens is also known as diverging, lens because it diverges a parallel beam of, light rays passing through it.,  A double concave lens is simply called, concave lens., Image formation by Lenses, Image formation by a convex and concave lens is, given separately., , Object, , Position of, , Image, , Image, , Location, , Image, , Nature, , Size, , Infinity, , At focus on, , Virtual, , Highly, , same side of, , and Erect, , Diminished, , Diminished, , Ray Diagram, , lens as object, Beyond, , Between focus, , Virtual, , Infinity and, , and optical, , and Erect, , Zero, , centre on the, same side of, lens as object, , Page | 6, The, https://play.google.com/store/apps/details?id=com.wonderslate.winners, , Winners Institute Indore, 9009428505, 8889009100

Page 7 : Page | 7, The, https://play.google.com/store/apps/details?id=com.wonderslate.winners, , Winners Institute Indore, 9009428505, 8889009100