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now very common illustration which is very useful to understand the field of view is.
the minimum length of mirror require to see self image. say we are given with a. large
size vertical mirror. which is placed on horizontal ground and in front of the mirror say. an
observer is standing. and in this mirror we can say observer is standing at a distance
x, at the same distance behind the mirror x, the image of this observer will be obtained.
which is of same size. as that of observer because it is a plane mirror. in this situation
say if this observer is willing to see his full image. we are required to find the minimum
length of mirror which is require obviously if the mirror is full, suddenly he’ll be
able to see full image. now to see his full image. in the field of view of observer the
complete image the. shoes of, his image to the hairs of his image must be in the field
of view of this observer. so if we, create the field of view by. joining the eye of observer
to the, extremities of the image, like this. then we can say this is the field of view
of observer then he’ll be able to see the complete image. so if here this image is broken
from these 2 points a-and b. and the mirror. which is above and below. the segment a-b
is removed. even after that we can see he’ll be able to see the complete image. if the
height of observer is h, then the height of image will also be h as, in case of plane
mirror the, image obtained as exactly of same size. then in this situation we can see these
points are a-and b if eye of observer is, e and say these points are c and d which are
the top and bottom points of the image. and here we can write in. triangle, e-c-d. in
this triangle a-b is a line which is parallel to the base and which is that the half. altitude
of this triangle. e-c-d so in triangle e-c-d we can directly write that a-b is equal to
half of c-d that basic triangle properties you already studied. and here c-d is h so
this must be h by 2. this is the minimum, length of the mirror which is required if
it is placed at this position, a-b. then through this mirror observer will be able to see his
complete image. so here we can write down a note that. minimum length. of mirror required.
for a man. to see. his complete image. is half of. his height. if his height is h then
h by 2 is the minimum length. of. mirror size required. through which he’ll be able to
see his complete image this quite a useful, concept. you must keep in mind if we just
wish to see how he is able to see, then we can directly write that. the light ray which
originated from the top most point. will be reflected from the edge of mirror and gets
into his eye. so he feels that the light rays coming from the image of his hairs similarly
light rays from shoes. will incident on the edge of the mirror and will reach. his eyes
and he’ll feel that the light rays are coming from the. image of the shoe. now in this situation
all those light rays which are originating from various points within the body of this
observer will gets reflected from the. mirror a-b and final gets into the eye of observer
and he’ll feel that the light rays are coming form the image of his body that’s why he
is able to see his complete image. this logic is also very useful, in handling various kind
of numerical applications.