Image formation Concave Mirror - Light Reflection & Refraction, CBSE Class

hello friends this video on light
reflection and refraction but six is
brought to you by example art form no
move here from example please make sure
that you have watched all the videos in
part 5 before going ahead with part 6
now we will first focus on the image
formation by concave mirrors so we will
first talk about only about the concave
mirror so let us take the first scenario
where we assume that an object is placed
at infinity so how would be the ray
diagram in case of object at infinity so
when the object is has infinity that
means the incident rays are coming from
some distant point so we assume that
parallel rays of light are coming right
because the object is at a very far off
distance we don't know there so let us
suppose that there is one ray which is
falling or blink if he wants the pole so
what will happen how will it get
reflected if this is my conceiving train
how will it get reflected it will get
reflected obliquely right now let us
suppose there is another ray which is
coming from the object such that it
passes through the centre of curvature
so this ray will meet the mirror
somewhere here let us suppose this is my
mirror so after reflection what will
happen it will go back along the same
path right now what do we know where is
an image form it is formed at a point
where the reflected Ray's need so here
this is one reflected ray and this is
another reflected ray
so both these rays meet at this point so
that means image is formed at this point
so this is my image right so this is the
image with respond so what kind of image
is formed we get a real image because in
this case the reflected rays actually
meet at this point so what is the nature
of the image it is a real image it is an
inverted image so if the email
would have been formed like this it
would have been an erect image but since
it is formed the other way around
so it is an inverted image so we got an
invert real image inverted image and
what is the location of the image it has
formed at the focal length so that means
when the object is at infinity in front
of a concave mirror a real and inverted
image will be formed at the principal
focus of the concave mirror right okay
now let us look at the second scenario
where we see that the object is beyond
the center of curvature that means the
object is far from the mirror but it is
not that far
so that means it is somewhere beyond the
center of curvature and it is assumed
that the object is somewhere here so let
me denote this a B if we call the object
as a B this some object so now in this
case let us suppose there is a ray of
light which goes parallel to the
principal axis and falls on the mirror
so according to rule number one what
will happen a ray of light
fabula to the principal axis after
reflection passes through the principal
focus so this is how it will go after
the reflection now let us suppose there
is another ray which passes through the
center of curvature suppose there is not
the rail which passes through the center
of curvature and falls on the mirror so
what will happen to this ray after
reflection it will retrace the same path
so what is the point which is the point
where the two reflected rays are meeting
this is the point so that means an image
will be formed here so let me call this
image as B - a - now what is the nature
of this image this is real again because
the Rays are actually meeting at this
point it is inverted again right what is
the location of the image so if the
object is located beyond the center of
curvature then the image is formed
between the principal focus and the
center of curvature what about the size
of the image if you look at it the size
of the
image is smaller than the size of the
object the length a B is greater than
the length B - J - so the image is
diminished that means it is smaller in
size than the object so this is the
nature of the image formed when the
object is placed in front of the concave
mirror beyond its centre of curvature so
I guess now you are understanding you're
getting an idea how do we plot array
diagram and these diagrams are known as
rainy diagrams because we are playing
with the rays of light so it is called
the Bay diagrams let us look at the
third case where we see that the object
is placed at centre of curvature so if
you see we are gradually bringing the
object closer to the concave mirror
right before it was first it was at
infinity then it was beyond the centre
of curvature now it is at the center of
curvature so that means let us suppose
this is my object so let me call this
object as a D so here also now it is not
necessary that you have or to assume but
the first ray to be parallel to the
principal axis and then passing through
the focus you can consider any of those
four rules which I mentioned you can
consider that the ray of light from this
is passing through the principal focus
and after reflection whose parallel to
the principal axis you can assume that
it falls off neatly and then goes back
and you can take any of the two rules
any out of those four rules you can
consider any two or anything and you
will see that all the reflected rays
will meet at a point and at that point
image will be formed right so now in
this case let us again suppose that
there is one ray of light which is going
parallel to the principal axis and as
per rule number one it passes through
the principal focus now let us put the
another rule here is rule number two
that means that another ray is passing
through the principal focus so after
reflection it will go parallel to the
principal axis so what do we see they
meet at this point that heals and
which will be formed here and we call
this image as B - a - so what is the
nature of this image it is again real
because the Rays are actually meeting at
this point it is again inverted right
what about the location the location is
center of curvature that means if the
object is located at the center of
curvature the image will also be formed
at the center of curvature and what
about the size if you look at it the
size of the object and the image are
comparable that means they are almost of
the same size so this describes the
nature of the image formed when the
object is at centre of curvature let us
look at the fourth scenario where we
want the object to be placed between the
center of curvature and the principal
focus so now the object is still nearer
to the mirror so this is my object a B
so here also let me ask you menu two
rules array of light parallel to
principal axis after reflection passes
through the principal focus right
another day of light passes through
principal focus and after reflection
goes parallel to the principal axis well
in this case the diagram is not launched
it properly because in this case the two
rays of light will meet at a point which
will be beyond the center of curvature I
mean since here I am plotting the lines
I mean I am NOT plotting it correctly
with measuring scales so it is not
meeting at the exact point otherwise
this point should be such that it is
beyond the center of curvature so that
means you have which V Dash and a dash
so in this case what kind of image do
you get it is again a real image
inverted image located beyond the center
of curvature and what about the size in
this case the image is enlarged if you
see the length of the image is greater
than the length of the object so you get
an enlarged or magnified image now let
us bring the object even more near to
the mirror so let us place the object at
the principal focus so now we have our
object at F so in this case again ray of
light parallel to the principal axis
after reflection passes through the
principal focus right another ray of
light let us suppose it falls obliquely
to the pole making some angle theta so
after reflection it will go obviously so
in this case what do we see the two rays
are going almost parallel and they do
not appear to meet immediately so that
needs going to be as UV as shown that
these two rays since they are going
parallel so they will meet at some in
finite points so we say that the image
is formed at infinity so here the image
at infinity because the Rays are going
parallel so here
not drawn incorrectly so this line will
go parallel to this line so the image in
this case is formed at infinity and what
kind of image will be formed real image
because but doesn't matter how how much
you were fine but the rains will
actually meet so you will get a real
image and the image will also be
inverted because it will meet somewhere
here that means it will meet somewhere
below the principal axis and so you will
get an inverted image and what would be
the size the science would be enlarged
that's because the farther away it meets
the greater becomes the size of the
image right so it will be enlarged let
us try to bring the object little world
closer so let us place the object
between the pole and principal focus so
what happens in this case a ray of light
fan will passes through the principal
focus another ray of light falls on the
pole obviously and then goes back so in
this case what do we see that the two
rails don't go parallel in state the
diverge away from each other so that
means there is no possibility that they
will meet up in future if the two rays
are going parallel we assume that they
will meet up at some infinite point but
if they are moving away from each other
there is no possibility that they will
ever meet so in this case what do we do
we extrapolate it at the back and we see
that they appear to meet at this point
and then we say that this is my image so
we say this a - V - is the image formed
so in this case what is the nature of
the image it is virtual because in this
case the Rays do not meet actually the
image is correct what is the location of
the image in this case the image is
formed on the other side of mirror till
now it was forming the image was getting
formed on the same side of the mirror
now it is gone on the other side of the
mirror what about the size of the image
it is enlarged right so I hope you
understood how we
how we decide the image formation by a
concave mirror that means there will be
an image formed what would be the nature
of that image what would be the size of
the image all those things can be
decided with the help of Ray diagrams so
now this chart tells you till now we
have discussed all different of object
locations so this chart is a review of
whatever we have derived so far so when
the object is at infinity the image is
formed at the focus focus
nature is real and inverted and the size
is diminished as the object is brought
little closure that so here if you
observe you see that as the object is
brought closer to the mirror the image
formed is goes away from the mirror
let's see the object is brought nearer
from infinity to focus and the image
goes from infinity from focus to
infinity as the object is coming nearer
the image is going away and as the
object is coming nearer the image is
increasing in size because when the
object was in infinity the image was
diminished then then gradually the image
become of the same size then it started
becoming enlarged so the closure the
object the bigger is the size of the
image thank you please visit exam few
calm to watch free educational videos
try free online tests get the best
quality study materials study from the
best tutors and mentors and much more
thank you once again