Understanding Line Symmetry and Mirror Reflection Video Lecture | Mathematics (Maths) Class 7 (Old NCERT)

symmetry
in this module you will learn about line
symmetry and mirror symmetry
look at this dodge ma hell and the
Ravana malai they look so beautiful
aren't they these pictures of
architectural marvel are beautiful
because of their symmetry as here
certain figures are with evenly balanced
proportions when one shape becomes
exactly like another if you flip slide
or done it then the shape is said to be
symmetrical let us learn about line of
symmetry look at this picture
let us fold this picture into half can
you see this white line
a line of symmetry shown here in white
is the imaginary line where you could
fold the image and have both halves
match exactly here we can see that the
one half of the image is the reflection
of the other half image it is also known
as mirror line the line of symmetry also
called the mirror line can be in any
direction let us learn line symmetry
with one more example here is a paper of
a rectangular shape let us first fold it
so that we get a centre line is this
fold a line of symmetry why yes it is
one side of the shape looks exactly like
another if you fold it
let us learn about blot painting method
take some watercolor and a sheet of
paper first pull the sheet into half so
that we get a centerline now open it can
you see the line in the middle
we can see that this line divides this
page into two equal parts
now put few drops of ink randomly on the
one half of the paper then fold the
paper back again and press it down now
open the paper we can see that the ink
has spread over and formed a pattern
similarly draw a butterfly using this
method for that paint half of the
butterfly on the one side of the fold of
drawing paper
we'll use three different paint colors
to make it look more beautiful now fold
the paper press it down and open it here
is our butterfly painting ready
isn't it beautiful if we observe we can
see that both the halves are identical
is the resulting figure symmetric let's
check if we place a mirror in between
the painting we see that half of the
image on the paper is exactly like the
other half of the image on the mirror
ends this image is said to be symmetric
as here we see line of the symmetry we
see that by folding the paper into half
we get the exact pattern of 1/2 on the
other half of the paper in simple words
we can say that we got mirror images of
each other
do you know there are different types of
line symmetry like vertical line
symmetry horizontal line symmetry or
diagonal line of symmetry can you see
this right direction arrow it is in
horizontal line symmetry look at this
verse it is in vertical line symmetry
now what about the star shape it has
multiple lines of symmetry it has a
diagonal line of symmetry
it also has vertical line of symmetry
look at this guide can you tell me how
many lines of symmetry does the guide
shape have this guide shape has only one
line of symmetry that is vertical line
of symmetry
can you read this word try ok now let's
keep a mirror in front of it now read
this with the help of the mirror can you
read now great the word is reflection
we all like to stand in front of the
mirror we all can see our own image in
the mirror but have you noticed one
thing that when you stand in front of
the mirror you and your image are always
at the same distance from the surface of
a mirror this is called mirror line you
can see that your left and the right
sides appear inverted in a mirror
it shows mirror symmetry with the mirror
line being the line of symmetry the line
of symmetry is related to mirror
reflection an object and its mirror
image are equal in shape and size look
at the letter B let us keep this letter
in front of the mirror can you see some
changes in the letter that appeared in
the mirror yes we can see that the
letter B appears reversed in a mirror
let us try some more letters letter C D
E and F we see that all these letters
appears reversed in a mirror
also when an object is reflected there
is no change in the lens and angles that
is the lens and angles of the object and
the corresponding lens and angles of the
image are the same
but there are some letters which remain
same in the mirror image let us try to
see letter e in the mirror
we can see that there is no change in
its mirror image it does not look
reversed or inverted try letter H
amazing here also we see the mirror
image of letter H is the same do you
know the letters e H I M o t u v w x and
y appear the same in the mirror images
whereas letter b c d e f g j k l n b you
are s of the alphabet appear reversed in
the mirror image because the letters
written from right to left appears as
written from left to right in their
mirror image this concept is used in
writing word ambulance in reverse manner
on the ambulance vehicle so that the
other vehicles while driving can read it
correctly in their rear mirror
we all like to draw a rangoli look at
this rangoli pattern isn't it beautiful
can you find some symmetry pattern in
this rangoli yes we see some symmetry
pattern in this rangoli to the line of
symmetry formed in this rangoli makes it
look more beautiful symmetry has plenty
of applications in real life we can see
symmetry in art architecture textiles
designing science and nature - etc
let us revise all that we learned in
this module on symmetry
you