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€ 6(4).pdf, , , , . Umbra - Region of total darkness, where no ray of light enters., Penumbra - a region of partial, darkness, surrounding the umbra., Some light reaches this region., , If a beam of light falls on the mirror,, the entire beam is reflected in only, one direction. This is called regular, reflection. When the ray or a beam of, light falls on an object with an uneven, surface, they get reflected to different, directions. This is called irregular, reflection of light., , Take three equal size cardboards., Make a very small hole through the, centre of each. Make them stand on, a table in such a way that their holes, are in a straight line. light a candle at, one side of the table in such a way that, the flame is in line with the holes., Look from other side. You can see, the flame. But if you disturb middle, cardboard then you will not be able, to see light. Thus light travels in a, straight line., , The best reflection is formed by a plane, mirror, for being the smooth surface, the light is reflected in one direction., The steel plate and a bow] full of water, are not smooth surfaces, so the light, is reflected in all directions and the, image is not proper., , Since the shadow itself is dark in, colour. So, when during night it is, already dark we are unable to see the, shadow clearly., , Principle : To show rectilinear, propagation of light rays., Construction : Take a cardboard box, with one end open and other covered., Paint it black from inside., , Cover the open end with a smooth, tracing paper to act as the screen., , , , 45, , 45/88, , Make a hole with a pin on other side., , , , A, , Pinhole camera, , Working : Stand in a darkroom and, point the hole towards the objects, outside a window. The objects should, be in bright light., All the images will be inverted, and, diminished in size., HOTS, Page 137, 1. Total lunar eclipse can be observed, over a much larger area of earth than, total solar eclipse. It is because moon, is much nearer to earth than sun, and earth is far bigger than moon, to obstract light coming from sun., Earth totally obstract light from sun, reaching to moon and no part of moon, could receive light. Lunar eclipse occur, on full moon day., Yes, an object can form two more, shadows at the same time. When light, incident on the object from different, sources provided object and sources, are not on same plane., Shadow of an object is always black, (dark) and does not depend on the, colour of source light falling on the, object., ACTIVITY CORNER, Page 137, , Group Discussion:, Do it yourself, Think and Tell:, , 1. Bulb, , 3. Shadow, , 2. Beam, 4. Opaque