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A source of light. For example, if you hold a book in front of a wall in a dark room,, you will not be able to see its shadow on the wall, If you allow torch light to fall, on it, you will see its shadow on the wall., An opaque object. For example, if you move the curtains from the front of a glass, window during the daytime, no shadow of the glass will be formed because glass, is not an opaque object which can obstruct the path of the light., A screen on which the shadow is to be formed. If you place a book on a table, in the centre of a room and light a torch on it, no shadow will be formed. If you, hold a screen behind the book, the shadow of the book will be formed on it., (b) Apinhole camera is a camera without a lens. It consists of a light proof box with a tiny, hole on one of it sides. As the light falls on the pinhole, it forms an inverted image, of the object on the opposite side of the box., A pinhole camera is based on the rectilinear propagation of light., (c) No, reflection cannot take place in absence of light. Light is necessary for reflection, to take place. It is only the light rays that bounce back from an object and enable us, to see it. Reflection of light by a mirror gives rise to the formation of images. If we, stand in front of a mirror in a dark room, we will not be able to see our image in the, mirror. But we switch on lights, we will be able to see our image in the mirror. This, proves that light is necessary for reflection to take place., (d), Image, Shadow, 1. It is of the same colour as the object. 1. It is always black in colour., 2. It gives all details of the object., 2. It gives no details of the object., 3. Image formed undergoes lateral, inversion, 3. A shadow formed can never be, laterally inverted., (e) (i) Luminous objects: Luminous objects are objects like the sun, stars, burning candle,, firefly, etc., that emit light of their own., Non-luminous objects: Non-luminous objects are objects like table, chairs, dogs,, trees, etc. that do not emit light of their own. The heavenly bodies like planets, and moon are also non-luminous objects., (ii) Transparent objects: Transparent objects like clear water, clean glass and air allow, light to pass through them completely. Hence, we can see through these objects, clearly., Opaque objects: Opaque objects are objects that do not allow light to pass, through them at all. For examples: wood, book, metals, bricked wall. We cannot, see through them at all, (iii) Regular reflection: The reflection of light rays from a smooth, shiny surface is, regular and in one direction. Such a reflection is called regular reflection., Irregular reflection: The reflection of light rays from a rough surface is irregular, and in different directions. Such a reflection is called irregular reflection. It is also, called diffused reflection., 83