Page 1 : to converge. partially are called translucent material. |, , www.tnpscjob.com, , Term-3 EM unit Lind 9 &, , aes ® LH a, , , , example, we cannot see the image of someone Opaque Material:, , who stands behind a rough window glass, Materials that are not able to allow li, because it allows only a part of light from the to pass through, are called opaque mater, person. Example: Wall, thick card board, stone, etc., , of EE, , Let's categorize transparent material, translucent material and opaque material among the given, materials, , (Clear plastic ruler, cellophane paper , some water in a glass jar, tissue paper, drinking glass,, beaker, tap water, kerosene, coconut oil, note paper, card board, milk, diluted milk, aluminum, foil, thick colored plastic lid, rough glass piece, measuring glass with water, wooden piece), , Place all the materials given above in the dark room. Focus a torch light on one side of each, material. Inspect the light coming out at the other side of each material and then classify the, materials in the table., , S. No Transparent Material Translucent Material Opaque Material, , is called as umbra. When an opaque object, , Shadows, , How areshadows formed? placed in the path of light coming from a bre, , —— source of light, a small umbra will appear on |, As we saw earlier, light . ., screen and an illuminated shadow area appe, , Ao, , I1V3E5 around umbra. This illuminated shadow a, , is obstructed by certain, , , , materials. Light travels in a, aa. 5 : ; Fick is called as penumbra. The penumbra alw:, straight line. Hence it cannot go around suc, , 8 . surrounds the umbra. The umbra is the dark, objects. That is why we see shadow. Shadow is . ., . a : part of a shadow. In this part, light rays |, always against, opposite side of light source. It ., . . . completely prevented by the opaque object. 1, is caused by opaque objects that stop light from, , . lighter shade of shadow is the penumbra., propagating., , Properties of shadow, , Parts of shadow 1, All objects do not form shadows. Only opac¢, , When an opaque object is placed in the objects form shadows, path of light from a point source, a uniform dark 2. Shadows will be formed in the opposite s, shadow will appear on the screen. This is shadow of light source, 10, , www.tnpscjob.com, Term-3 EM unit L.indd 10 Cy, , eee ® Ln a