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( LiGHT #8 [: gor) °§, , from the tee enter the eye, , of the pe, , a TSOT, , wth ope (even though the tre 1 (or observer, a », , ec ., wll 7 CANNOL be seen directly), Ppa periscope, te IOP Mirror reflects tight, : ic of a periscope demonstrates that refle, yo : slains how reflection from tio plane m, at’, A got of the Uses of Periscopes ar, A periscope is used to see over t, ii) A periscope is used by soldier, (over the ground)., a) \ periscope is used b ., ij) A perisc Y ANAvY officer ces., the sea (even though the ae er sitting in, The fact that reflecteq light can, ., head at a hair dressey’s, pis h sh, gresset holds a small p], , of tree through, ), it is possible to see the image of ;, , and the bottom mirror reflects the ‘reflected light mG i, cted light can be reflected again. The working of a Pe iredit ;, irrors enables us to see objects which are not visible airecty., © Given Below ; ', , he heads of a crowd (say, as in a football match)., , res ‘ sin si e, ® Sitting in a trench (or bunker) to observe the enemy activities outsid, , , a submarine to see ships over the surface of water In, , atine itself may be submerged under water)., , be Teflected again enables a person to see the hair cut at the back of, , ane a This happens as follows : After giving the hair cut toa person, the me, dis reflected by th; rror behind the head of the person. The light coming from hair at the bac, , of hea Y this Small mifror on to a big mirror which is in the front of the person. This big, , ror rete ie Pein light’ again due to which the person can see the image of the back hair of his, head showing how the hair have been cut at the back side of his head., , Multiple Images, , We Know that a plane mirror forms only a single image of an object placed in front of it. We will now, describe what happens when an object is placed between two plane mirrors which are inclined at an angle, to each other. When two plane mirrors are kept inclined at an angle, they can form multiple images of, an object. This is because the image of object formed in one plane mirror acts as object for the other plane, , mirror. It has been found that if two plane mirrors are intclined at an angle x, then the number of images, formed in them is given by the formula :, , No. of images formed = oor il, , By using this formula, we can calculate the number of images formed (or seen) when two plane ee, are inclined at angles of 180°, 120°, 90°, 60°, 45° and 0°, respectively. As an example, let us calculate :, _number of images formed in two plane mirrors inclined at an angle of 90°. In this case the angle betwee, two plane mirrors (x) is 90°. So,, 360°, No. of images formed = “op -1, =4-1, =3, Thus, two plane mirrors inclined at an angle of 90° form fliree images of an object placed between, them., , When the two plane mirrors are inclined at an angle of 90°, they are said to be at right angles to each, other. So, we can also say that the two plane mirrors arranged at right angles to each other form three, i et them at right angles to, , then we will see three, , , , , , , , , each other (with their edges touching), «, images of the coin in the two plane mirror:, , , , We can also do the calculations fi, mirrors are inclined at angles of 180°,