Class 12 Exam > Class 12 Videos > L46 : Simple Microscope - Ray Optics, Physics, Class 12
L46 : Simple Microscope - Ray Optics, Physics, Class 12 Video Lecture
FAQs on L46 : Simple Microscope - Ray Optics, Physics, Class 12 Video Lecture
| 1. What is a simple microscope in ray optics? |  |
| 2. How does a simple microscope work in ray optics? | |
Ans. A simple microscope works based on the principle of refraction of light. When an object is placed close to the convex lens of a simple microscope, the lens refracts the light rays coming from the object. These refracted rays converge to form a magnified virtual image that can be seen by the eye.
| 3. What is the magnification produced by a simple microscope? | |
Ans. The magnification produced by a simple microscope can be calculated using the formula: magnification = 1 + (D/f), where D is the least distance of distinct vision (usually taken as 25 cm) and f is the focal length of the lens used in the microscope. The magnification is usually found to be greater than 1.
| 4. What are the advantages of using a simple microscope? | |
Ans. Some advantages of using a simple microscope include:
- Portability: Simple microscopes are compact and lightweight, making them easy to carry and use in various settings.
- Low cost: Compared to complex microscopes, simple microscopes are relatively inexpensive, making them accessible to a wider range of users.
- Ease of use: Simple microscopes are straightforward to operate and require minimal setup or adjustments.
- Real-time viewing: Simple microscopes provide real-time magnification, allowing users to observe objects directly without the need for image capture or processing.
| 5. What are the limitations of a simple microscope? | |
Ans. Some limitations of a simple microscope include:
- Limited magnification: Simple microscopes are generally limited in their magnification capabilities compared to complex microscopes.
- Shallow depth of field: The depth of field of a simple microscope is typically narrow, meaning only a small portion of the object can be in focus at a time.
- Limited resolution: Simple microscopes may not provide high-resolution images, which can limit the ability to observe fine details.
- Distortion: The image produced by a simple microscope may suffer from some distortion, particularly towards the edges of the field of view.
Text Transcript from Video
hello friends this video on ray optics
part 46 is brought to you by exam comm
know who fear from exam please make sure
that you have watched all the videos
till patch 45 before going ahead with
part 46 let us now talk about the next
optical instrument that is the
microscope so what is a microscope you
have seen this maybe you would have
worked with microscope in your science
labs so it is an instrument that gives
an enlarged image of a minut object so
that means you have a very small object
and you get a very magnified image of
that object so the magnification plays a
very important role in case of a
microscope so even inside the microscope
there is nothing but a combination of
lens some lenses only there inside the
microscope which magnifies the image to
that extent so let us see now there are
two types of microscopes one is instinct
with microscope and the other one is a
compound microscope so now we will
discuss first we will discuss the simple
microscope and then we we see that why
was the simple microscope not enough or
why was there a need for another
advanced microscope which was known as
the compound microscope so let us start
with the simple microscope simple
microscope is nothing but a convex lens
that's it so if an object is placed very
near to a convex lens the image which is
formed is a very enlarged as well as
direct image so this that is what is the
purpose of a microscope right in
microscope we want to view an object and
generally we view with very closely for
example you would have seen in the
microscope in your lab that if you want
to see some tiny object you don't keep
that object miles away and then trying
to view it with the microscope so you
keep that object closer to the
microscope and then you view it that
makes the object the distance of the
object from the microscope is very near
so the object is very closer to the lens
and what we want we want a magnifying as
in it image so for this context lens is
a suitable lens I have already discussed
about these and image formation if this
is my object array parallel to the
principal axis after refraction passes
through the focus another ray passing
through the optical center goes I'm
deviated so these two rays if go if they
go ahead it looks like they will are
they are going away from each other so
if we join them backwards using these
dotted lines we see that they appear to
meet at this point so this gives rise to
a magnified direct image so this was the
simple microscope so that means simple
microscope was nothing but a convex lens
a simple convex lens you would have seen
sometimes if you have ever been to an
astrological obscene that they have got
a magnifying glass right they call it a
magnifying glass
they give that glass on your palm and
then they will see the lines of your
pumps so then that is all that is
nothing but a simple microscopy that is
nothing but a simple convex lens which
gives an a magnified image of a closure
object right so now it was been observed
that the magnification given by a convex
lens alone is not enough there are so
many minut things which we want to
observe for example there are minut
organisms like bacteria or small small
atoms and so many things so many tiny
objects are there which have now become
visible because of high resolution
microscopes so they felt that the
magnification provided by this simple
microscope was not enough so what they
did they tried to do something to
increase the magnification now we will
look at the magnifying power of a simple
microscope I mean why did we just now I
told you right
that simple microscope is nothing but a
convex lens with the object placed very
near to the lens so why don't we why did
we choose this arrangement so let us
look at the magnifying power of this
simple microscope we will see that how
the magnifying power in this scenario is
maximum and what does the limitation of
simple microscope avoid this Maxim the
magnifying power cannot be increased to
a very high value so let us have a look
at that let us consider two scenarios
here in the first scenario where do we
see that the object is placed at the
focus and the image is formed at
infinity so in this first scenario image
is at infinity and the object is
situated atom focus and in the second
scenario it is told that if an object is
placed at a distance which is equal to
the least distance of distinct vision so
this represents least distance of
distinct vision that is also known as
near point so if an object is placed at
a distance D in that case the object is
very clearly and distinctly visible to
the eye now what happens in this case
when the object is placed at the focal
at the principal focus the image is
formed at infinity in that case the eye
is the is move is the most relaxed
position the eye is not at all strained
right because in that case the ciliary
muscles are relaxed so that the focal
length is at its maximum value and the
image is formed on the retina right in
this case when the object is at a the
least distance of distinct vision even
though the object is visible clearly by
the eye is little strange when compared
to the first scenario so now let us try
to calculate the magnification in this
case when the object when the object is
situated at focus and the image is
formed at infinity now in this case the
angle which is subtended on the eye is
Theta I right so theta I or let me call
it as theta so theta is the angle which
is subtended on the eye so from here we
can say that since we are dealing with
small angles
so instead of tan theta we can write it
as theta which is equal to what is this
theta in this if you look at this
triangle you can say that theta is equal
to H by L and what will give this theta
not in this case it will be nothing but
H by D right so now if I want to compare
now if not if I want to calculate the
magnification of a simple microscope
then let me consider the scenario of the
simple microscope in simple microscope
what do we do we bring the object even
more closer than the focal length so
right now the object the focus may be
somewhere here so the object is brought
even closer than the principle focus in
that is what happens and we Nations
formed right near in such a way that the
image is formed at a distance equal to
capital T that means this is the least
distance of distinct region so this is
my image and this is my objects right
now the image it as is at least distance
of distinct vision right so in this case
the eye is strained
the eye is definitely strained because I
told you here also the eye strain but at
least it can view the image clearly and
properly so now let us talk about
magnification right so when we consider
these two considering this scenario what
do we see here in this case we see that
D is greater than F in this case
now if D is greater than F this will
imply that theta is if D is greater than
F this would imply that theta is greater
than theta naught right so when I talk
about magnification right because this
scenario is nothing but a combination of
these two scenarios right so we can say
that so when we are calculating the
magnification my
Asian is nothing but theta by theta
naught so this is H by F divided by H by
D so which comes out to be D by F so the
magnification is greater than 1 if D is
greater than F so this is what we
achieve that means we can increase the
magnification to greater than 1 that
means the image will be larger in size
than the object if capital D that is the
least distance of distinct vision is
greater than the focal length right so
that means the focal length has to be
smaller as well as we have to make the
arrangement in such a way that the image
is formed at least distinct of distinct
vision so how is it possible that we can
increase this magnifying power even more
so for that what we do we decrease the
distance of the object so the object is
now placed even before the focal length
let us suppose this was the focus now
the object is placed even before the
focal length so in this case what will
happen a virtual image will form at a
near point at this point I is strange
but the image is seen properly so now in
this case let us try to apply the thin
lens equation let us 1 by V minus 1 by U
is equal to 1 by F now in this case what
is V image is formed at a distance D
that is minus T what is u U is nothing
but minus u let me say this Lu is you
not see this will be Q naught therefore
we can write minus 1 by D plus 1 by u
naught is equal to 1 by F now if I
multiply D on both sides we get minus 1
plus D by u naught is equal to D by F or
we can say d by u naught is equal to 1
plus D by F right so now let us try to
calculate the magnetic
in case of this simple microscope so
what will be magnification it will be
nothing but theta divided by theta
naught so what is Theta theta in this
case what is Theta in this case it is
nothing but h divided by u naught
because U is the distance so this is
this would be theta naught right and MSR
this would be theta and what does theta
naught theta naught is nothing but the
angle subtended by the image at this
point which is equal to H divided by
capital D so theta naught will remain
the same because theta naught talks
about the scenario then some object lies
at a distance capital D from the eye so
this theta naught will be H by D so from
this we get magnification is equal to D
by u naught and from this expression one
we know that D by u naught is 1 plus D
by F so this expression defines the
magnification of a simple microscope so
what do what can we predict from this
equation we can see that N and increase
only up to a certain limit beyond that
the image becomes very defective because
if you look at it it is 1 plus D by F
now the difference that the the factor D
by F actually determines how large the
magnification can be and it is seen that
the magnification can only go up to a
certain limit and after that if the
image comes out to be very large in that
case the image is very much defective
because here we have assumed that the
image is at least distance of distinct
region now if we try to bring the object
even more closure may be the email
silence will increase but since if the
image also starts coming closure in that
case the region will get blurred so thus
it was found that the magnification
factor became a limitation for simple
mic
it was seen that it can increase only up
to a certain limit beyond which the
image turns defective so there came into
picture thank you please visit exam
viacom 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
part 46 is brought to you by exam comm
know who fear from exam please make sure
that you have watched all the videos
till patch 45 before going ahead with
part 46 let us now talk about the next
optical instrument that is the
microscope so what is a microscope you
have seen this maybe you would have
worked with microscope in your science
labs so it is an instrument that gives
an enlarged image of a minut object so
that means you have a very small object
and you get a very magnified image of
that object so the magnification plays a
very important role in case of a
microscope so even inside the microscope
there is nothing but a combination of
lens some lenses only there inside the
microscope which magnifies the image to
that extent so let us see now there are
two types of microscopes one is instinct
with microscope and the other one is a
compound microscope so now we will
discuss first we will discuss the simple
microscope and then we we see that why
was the simple microscope not enough or
why was there a need for another
advanced microscope which was known as
the compound microscope so let us start
with the simple microscope simple
microscope is nothing but a convex lens
that's it so if an object is placed very
near to a convex lens the image which is
formed is a very enlarged as well as
direct image so this that is what is the
purpose of a microscope right in
microscope we want to view an object and
generally we view with very closely for
example you would have seen in the
microscope in your lab that if you want
to see some tiny object you don't keep
that object miles away and then trying
to view it with the microscope so you
keep that object closer to the
microscope and then you view it that
makes the object the distance of the
object from the microscope is very near
so the object is very closer to the lens
and what we want we want a magnifying as
in it image so for this context lens is
a suitable lens I have already discussed
about these and image formation if this
is my object array parallel to the
principal axis after refraction passes
through the focus another ray passing
through the optical center goes I'm
deviated so these two rays if go if they
go ahead it looks like they will are
they are going away from each other so
if we join them backwards using these
dotted lines we see that they appear to
meet at this point so this gives rise to
a magnified direct image so this was the
simple microscope so that means simple
microscope was nothing but a convex lens
a simple convex lens you would have seen
sometimes if you have ever been to an
astrological obscene that they have got
a magnifying glass right they call it a
magnifying glass
they give that glass on your palm and
then they will see the lines of your
pumps so then that is all that is
nothing but a simple microscopy that is
nothing but a simple convex lens which
gives an a magnified image of a closure
object right so now it was been observed
that the magnification given by a convex
lens alone is not enough there are so
many minut things which we want to
observe for example there are minut
organisms like bacteria or small small
atoms and so many things so many tiny
objects are there which have now become
visible because of high resolution
microscopes so they felt that the
magnification provided by this simple
microscope was not enough so what they
did they tried to do something to
increase the magnification now we will
look at the magnifying power of a simple
microscope I mean why did we just now I
told you right
that simple microscope is nothing but a
convex lens with the object placed very
near to the lens so why don't we why did
we choose this arrangement so let us
look at the magnifying power of this
simple microscope we will see that how
the magnifying power in this scenario is
maximum and what does the limitation of
simple microscope avoid this Maxim the
magnifying power cannot be increased to
a very high value so let us have a look
at that let us consider two scenarios
here in the first scenario where do we
see that the object is placed at the
focus and the image is formed at
infinity so in this first scenario image
is at infinity and the object is
situated atom focus and in the second
scenario it is told that if an object is
placed at a distance which is equal to
the least distance of distinct vision so
this represents least distance of
distinct vision that is also known as
near point so if an object is placed at
a distance D in that case the object is
very clearly and distinctly visible to
the eye now what happens in this case
when the object is placed at the focal
at the principal focus the image is
formed at infinity in that case the eye
is the is move is the most relaxed
position the eye is not at all strained
right because in that case the ciliary
muscles are relaxed so that the focal
length is at its maximum value and the
image is formed on the retina right in
this case when the object is at a the
least distance of distinct vision even
though the object is visible clearly by
the eye is little strange when compared
to the first scenario so now let us try
to calculate the magnification in this
case when the object when the object is
situated at focus and the image is
formed at infinity now in this case the
angle which is subtended on the eye is
Theta I right so theta I or let me call
it as theta so theta is the angle which
is subtended on the eye so from here we
can say that since we are dealing with
small angles
so instead of tan theta we can write it
as theta which is equal to what is this
theta in this if you look at this
triangle you can say that theta is equal
to H by L and what will give this theta
not in this case it will be nothing but
H by D right so now if I want to compare
now if not if I want to calculate the
magnification of a simple microscope
then let me consider the scenario of the
simple microscope in simple microscope
what do we do we bring the object even
more closer than the focal length so
right now the object the focus may be
somewhere here so the object is brought
even closer than the principle focus in
that is what happens and we Nations
formed right near in such a way that the
image is formed at a distance equal to
capital T that means this is the least
distance of distinct region so this is
my image and this is my objects right
now the image it as is at least distance
of distinct vision right so in this case
the eye is strained
the eye is definitely strained because I
told you here also the eye strain but at
least it can view the image clearly and
properly so now let us talk about
magnification right so when we consider
these two considering this scenario what
do we see here in this case we see that
D is greater than F in this case
now if D is greater than F this will
imply that theta is if D is greater than
F this would imply that theta is greater
than theta naught right so when I talk
about magnification right because this
scenario is nothing but a combination of
these two scenarios right so we can say
that so when we are calculating the
magnification my
Asian is nothing but theta by theta
naught so this is H by F divided by H by
D so which comes out to be D by F so the
magnification is greater than 1 if D is
greater than F so this is what we
achieve that means we can increase the
magnification to greater than 1 that
means the image will be larger in size
than the object if capital D that is the
least distance of distinct vision is
greater than the focal length right so
that means the focal length has to be
smaller as well as we have to make the
arrangement in such a way that the image
is formed at least distinct of distinct
vision so how is it possible that we can
increase this magnifying power even more
so for that what we do we decrease the
distance of the object so the object is
now placed even before the focal length
let us suppose this was the focus now
the object is placed even before the
focal length so in this case what will
happen a virtual image will form at a
near point at this point I is strange
but the image is seen properly so now in
this case let us try to apply the thin
lens equation let us 1 by V minus 1 by U
is equal to 1 by F now in this case what
is V image is formed at a distance D
that is minus T what is u U is nothing
but minus u let me say this Lu is you
not see this will be Q naught therefore
we can write minus 1 by D plus 1 by u
naught is equal to 1 by F now if I
multiply D on both sides we get minus 1
plus D by u naught is equal to D by F or
we can say d by u naught is equal to 1
plus D by F right so now let us try to
calculate the magnetic
in case of this simple microscope so
what will be magnification it will be
nothing but theta divided by theta
naught so what is Theta theta in this
case what is Theta in this case it is
nothing but h divided by u naught
because U is the distance so this is
this would be theta naught right and MSR
this would be theta and what does theta
naught theta naught is nothing but the
angle subtended by the image at this
point which is equal to H divided by
capital D so theta naught will remain
the same because theta naught talks
about the scenario then some object lies
at a distance capital D from the eye so
this theta naught will be H by D so from
this we get magnification is equal to D
by u naught and from this expression one
we know that D by u naught is 1 plus D
by F so this expression defines the
magnification of a simple microscope so
what do what can we predict from this
equation we can see that N and increase
only up to a certain limit beyond that
the image becomes very defective because
if you look at it it is 1 plus D by F
now the difference that the the factor D
by F actually determines how large the
magnification can be and it is seen that
the magnification can only go up to a
certain limit and after that if the
image comes out to be very large in that
case the image is very much defective
because here we have assumed that the
image is at least distance of distinct
region now if we try to bring the object
even more closure may be the email
silence will increase but since if the
image also starts coming closure in that
case the region will get blurred so thus
it was found that the magnification
factor became a limitation for simple
mic
it was seen that it can increase only up
to a certain limit beyond which the
image turns defective so there came into
picture thank you please visit exam
viacom 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
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