1-1 Introduction to light microscope & magnification; Cambridge AS & A Level Biology (9700)
https://www.youtube.com/watch?v=dGfs6ka5NpE
[00:00] diving right into it we are going into
[00:03] diving right into it we are going into chapter one
[00:04] chapter one right now and chapter one is all about
[00:07] right now and chapter one is all about cell structure now before we talk about
[00:10] cell structure now before we talk about cell structure
[00:12] cell structure we are gonna have to talk a little bit
[00:14] we are gonna have to talk a little bit about something called
[00:16] about something called cell microscopy
[00:20] the word microscopy just basically
[00:21] the word microscopy just basically implies that we are going to be using an
[00:23] implies that we are going to be using an apparatus called the microscope
[00:25] apparatus called the microscope all right when we are talking about a
[00:28] all right when we are talking about a microscope
[00:29] microscope okay so what's the purpose of a
[00:31] okay so what's the purpose of a microscope we kind of know that the
[00:33] microscope we kind of know that the school
[00:33] school has a microscope called the light
[00:35] has a microscope called the light microscope and the microscope's
[00:38] microscope and the microscope's main function is just basically to
[00:40] main function is just basically to magnify
[00:41] magnify a specimen to magnify a specimen
[00:48] size and when we are talking about the
[00:50] size and when we are talking about the specimen
[00:51] specimen size okay it's not the actual specimen
[00:54] size okay it's not the actual specimen size by the way we are not
[00:56] size by the way we are not it's not like a a weird uh
[00:59] it's not like a a weird uh sci-fi ray gun to kind of enlarge the
[01:03] sci-fi ray gun to kind of enlarge the size of the actual specimen however
[01:06] size of the actual specimen however it is to magnify or the key word here is
[01:09] it is to magnify or the key word here is basically magnification we have to
[01:11] basically magnification we have to understand what the word magnification
[01:13] understand what the word magnification is and magnification is basically
[01:15] is and magnification is basically to enlarge the image size
[01:20] to enlarge the image size of a specimen right
[01:26] of a specimen right so in our eyes if we are looking at a
[01:29] so in our eyes if we are looking at a particular specimen and let's say that's
[01:31] particular specimen and let's say that's the actual size of a specimen that red
[01:33] the actual size of a specimen that red dot
[01:34] dot okay the actual size over there uh
[01:37] okay the actual size over there uh what happens is when we look at it
[01:40] what happens is when we look at it okay our brain will basically
[01:44] okay our brain will basically register a slightly bigger size okay
[01:47] register a slightly bigger size okay basically so this is what's supposed to
[01:50] basically so this is what's supposed to happen over here
[01:51] happen over here and in this case what we register is the
[01:53] and in this case what we register is the image size
[01:55] image size but how does this happen how does this
[01:58] but how does this happen how does this size
[01:58] size over here become this one over here
[02:02] over here become this one over here that process okay in between is called
[02:06] that process okay in between is called magnification and for magnification to
[02:08] magnification and for magnification to happen
[02:09] happen uh you can either use a light microscope
[02:12] uh you can either use a light microscope or you can use an electron microscope so
[02:14] or you can use an electron microscope so let's keep it very simple let's talk
[02:16] let's keep it very simple let's talk about
[02:17] about the light microscope first okay
[02:20] the light microscope first okay so for the light microscope
[02:25] i'm not gonna do the exact
[02:28] i'm not gonna do the exact uh structure of the light microscope i
[02:30] uh structure of the light microscope i mean that's not so important
[02:32] mean that's not so important what we have to know is we have to kind
[02:33] what we have to know is we have to kind of understand the fundamentals
[02:35] of understand the fundamentals first the fundamentals are as follows
[02:38] first the fundamentals are as follows when i say fundamentals i mean the
[02:39] when i say fundamentals i mean the basics we kind of have to know
[02:43] basics we kind of have to know how a microscope works
[02:46] how a microscope works imagine if you just have an object over
[02:48] imagine if you just have an object over here
[02:49] here this is just basically the specimen be
[02:51] this is just basically the specimen be it a cell
[02:53] it a cell whatever you're looking at it under the
[02:54] whatever you're looking at it under the microscope if you want to be able to
[02:57] microscope if you want to be able to look at a specimen you have to
[02:58] look at a specimen you have to understand
[02:59] understand how are we able to see something
[03:03] how are we able to see something if this is our eye you are only able to
[03:06] if this is our eye you are only able to see something
[03:07] see something if light was to hit the
[03:10] if light was to hit the specimen so that's light over that
[03:13] specimen so that's light over that light is able to hit the specimen and
[03:15] light is able to hit the specimen and the specimen must be able to reflect
[03:19] the specimen must be able to reflect the light into your eyes then your
[03:22] the light into your eyes then your photoreceptors in your eye detect the
[03:25] photoreceptors in your eye detect the light
[03:25] light it sends an impulse to your brain and
[03:28] it sends an impulse to your brain and your brain goes
[03:29] your brain goes i'm able to see the specimen basically
[03:32] i'm able to see the specimen basically that's what's supposed to happen but
[03:34] that's what's supposed to happen but let's talk about
[03:36] let's talk about what if the light was um let's say the
[03:39] what if the light was um let's say the object is like a
[03:40] object is like a transparent object if it's a transparent
[03:43] transparent object if it's a transparent object the light will just basically
[03:44] object the light will just basically pass through
[03:45] pass through and in that kind of situation the light
[03:48] and in that kind of situation the light will not be reflected
[03:49] will not be reflected and we will not be able to see anything
[03:51] and we will not be able to see anything at all
[03:52] at all that's what's supposed to happen so the
[03:54] that's what's supposed to happen so the first fundamental thing that you have to
[03:56] first fundamental thing that you have to understand
[03:56] understand is if you want to be able to see
[03:59] is if you want to be able to see something
[04:00] something if you want to be able to see something
[04:02] if you want to be able to see something the specimen
[04:03] the specimen interrupts the light
[04:06] interrupts the light and reflects the light
[04:13] into our eyes that's the first thing we
[04:16] into our eyes that's the first thing we must understand
[04:18] must understand so only when the light hits the specimen
[04:21] so only when the light hits the specimen and the light is reflected into our eyes
[04:23] and the light is reflected into our eyes we are able to see it
[04:25] we are able to see it fine now what's the big deal where does
[04:27] fine now what's the big deal where does magnification come in
[04:28] magnification come in magnification comes in when you kind of
[04:31] magnification comes in when you kind of put a lens
[04:32] put a lens over here now when you put a lens over
[04:34] over here now when you put a lens over here what actually happens is
[04:36] here what actually happens is it will go through the lens and in this
[04:39] it will go through the lens and in this situation over here when it enters our
[04:41] situation over here when it enters our eyes
[04:42] eyes our eyes will comprehend the specimen to
[04:44] our eyes will comprehend the specimen to be larger
[04:45] be larger than it actually is this over here is
[04:49] than it actually is this over here is the process of
[04:50] the process of magnification so this is the actual size
[04:53] magnification so this is the actual size of the specimen
[04:54] of the specimen over here and this is the image size
[04:57] over here and this is the image size pretty simple
[04:58] pretty simple fine now and
[05:02] fine now and if we were to look at the actual size
[05:05] if we were to look at the actual size over here
[05:10] over here if we were to make it bigger
[05:18] and this is the image size over here
[05:20] and this is the image size over here this is just the act of magnifying it
[05:23] this is just the act of magnifying it okay magnification equals
[05:30] you multiply the actual size and you'll
[05:32] you multiply the actual size and you'll actually get the image size
[05:34] actually get the image size over here so that's how they get the
[05:37] over here so that's how they get the formula
[05:38] formula the formula equals to
[05:42] actual times magnification equals to
[05:45] actual times magnification equals to image or you can also just rearrange it
[05:49] image or you can also just rearrange it where you can put magnification
[05:50] where you can put magnification equals to image over actual
[05:54] equals to image over actual that's how the formula comes to be so
[05:56] that's how the formula comes to be so let's try
[05:57] let's try a basic example basic example is as such
[06:03] if you have an actual size of a cell
[06:06] if you have an actual size of a cell which
[06:07] which is about for example 10
[06:10] is about for example 10 micrometer and based on the
[06:14] micrometer and based on the magnification of the cell
[06:16] magnification of the cell we are certain
[06:20] we are certain the diameter of the cell was when we
[06:23] the diameter of the cell was when we looked at it under the microscope it was
[06:24] looked at it under the microscope it was 10
[06:25] 10 millimeters so in this case they asked
[06:28] millimeters so in this case they asked you to calculate for example in the exam
[06:30] you to calculate for example in the exam what is the magnification basically
[06:33] what is the magnification basically magnification okay i'm just writing it
[06:35] magnification okay i'm just writing it like that
[06:36] like that so magnification equals to image over
[06:39] so magnification equals to image over actual
[06:40] actual and magnification equals to 10
[06:42] and magnification equals to 10 millimeters
[06:43] millimeters which is the one that you are looking at
[06:46] which is the one that you are looking at under the microscope okay
[06:48] under the microscope okay what you're looking at what you see and
[06:50] what you're looking at what you see and 10 micrometer
[06:51] 10 micrometer is the actual size now a lot of students
[06:55] is the actual size now a lot of students not a lot of students okay that's that's
[06:57] not a lot of students okay that's that's a bit of an unfair
[06:58] a bit of an unfair statement to make but a few students
[07:00] statement to make but a few students have a tendency to just
[07:02] have a tendency to just divide 10 millimeters to 10 micrometers
[07:04] divide 10 millimeters to 10 micrometers and they'll get the answer
[07:05] and they'll get the answer one and that is so wrong okay in maths
[07:09] one and that is so wrong okay in maths the units for the numerator and the
[07:11] the units for the numerator and the denominator they have to be
[07:13] denominator they have to be similar so you'll have to convert
[07:15] similar so you'll have to convert millimeter to micrometer and
[07:17] millimeter to micrometer and to convert millimeter to micrometer you
[07:19] to convert millimeter to micrometer you can just basically multiply it by a
[07:21] can just basically multiply it by a thousand
[07:23] thousand right and in this case it will be 10 000
[07:26] right and in this case it will be 10 000 micrometers divided by 10 micrometers
[07:32] micrometers divided by 10 micrometers and the answer in this case will be a
[07:34] and the answer in this case will be a thousand
[07:36] thousand that is the magnification right here
[07:38] that is the magnification right here okay
[07:40] okay it's quite straightforward and
[07:43] it's quite straightforward and of course the basic units that you'll
[07:45] of course the basic units that you'll have to know the units
[07:48] have to know the units in magnification uh
[07:58] in magnification uh rarely do we use centimeters but on the
[08:00] rarely do we use centimeters but on the off chance it might come out
[08:02] off chance it might come out we have millimeters we have micrometer
[08:05] we have millimeters we have micrometer i'm not best at writing micrometer over
[08:09] i'm not best at writing micrometer over there
[08:09] there okay and we also have a new one in igcse
[08:12] okay and we also have a new one in igcse you only had to learn these three
[08:14] you only had to learn these three scales but you also have to introduce a
[08:16] scales but you also have to introduce a new one nanometer because we're going to
[08:18] new one nanometer because we're going to be talking about
[08:19] be talking about organelles and organelles some
[08:21] organelles and organelles some organelles fall under the scale of
[08:22] organelles fall under the scale of nanometers okay
[08:24] nanometers okay conversion of centimeters to millimeters
[08:26] conversion of centimeters to millimeters is multiplied by 10
[08:28] is multiplied by 10 millimeters to micrometers multiplied by
[08:30] millimeters to micrometers multiplied by a thousand
[08:31] a thousand some books will put it as 10 to the
[08:33] some books will put it as 10 to the power of three this to this
[08:35] power of three this to this micrometer to nanometer again multiply
[08:37] micrometer to nanometer again multiply 10 to the power
[08:38] 10 to the power power of three or a thousand and
[08:41] power of three or a thousand and nanometer to micrometer
[08:42] nanometer to micrometer it's the opposite you just divide it
[08:44] it's the opposite you just divide it then divide the thousand
[08:48] then divide the thousand divide a thousand over here that's a
[08:51] divide a thousand over here that's a comma by the way that's not a decimal
[08:52] comma by the way that's not a decimal place it has a separator
[08:54] place it has a separator all right and this one is divided by 10.
[08:57] all right and this one is divided by 10. okay
[08:58] okay so these are the units that you'll have
[08:59] so these are the units that you'll have to know and you'll have to be able to
[09:01] to know and you'll have to be able to convert the
[09:04] convert the units effortlessly in the exam all right
[09:08] units effortlessly in the exam all right they give you like for example three
[09:09] they give you like for example three millimeters okay three millimeters and
[09:12] millimeters okay three millimeters and they ask you to convert it into
[09:14] they ask you to convert it into let's say micrometer so micrometer in
[09:18] let's say micrometer so micrometer in this case will be
[09:19] this case will be three millimeters times a thousand and
[09:22] three millimeters times a thousand and therefore
[09:23] therefore it is equivalent to 3 000 micrometers
[09:26] it is equivalent to 3 000 micrometers some students do ask do i have to put
[09:28] some students do ask do i have to put the separator in the exam no you don't
[09:29] the separator in the exam no you don't have to it's just a habit
[09:31] have to it's just a habit um if you just basically want to adjust
[09:33] um if you just basically want to adjust 3000 micrometer
[09:34] 3000 micrometer go ahead no problems with that and if
[09:37] go ahead no problems with that and if they do ask you to convert it into
[09:38] they do ask you to convert it into nanometer
[09:40] nanometer then what you'll have to do is you'll
[09:42] then what you'll have to do is you'll have to do three multiplied by a
[09:44] have to do three multiplied by a thousand
[09:45] thousand multiply by another thousand and in this
[09:48] multiply by another thousand and in this case it will be 3
[09:49] case it will be 3 million nanometers so
[09:52] million nanometers so the conversion is something that
[09:56] the conversion is something that we must be well versed with
[09:59] we must be well versed with that is just basically what
[10:01] that is just basically what magnification is all about magnification
[10:03] magnification is all about magnification is just
[10:05] is just taking the actual specimen this is the
[10:08] taking the actual specimen this is the actual specimen
[10:10] actual specimen and we magnify it using the lenses
[10:14] and we magnify it using the lenses in the microscope so that when we
[10:18] in the microscope so that when we view it under the microscope what we are
[10:20] view it under the microscope what we are looking at is
[10:22] looking at is an enlarged image of the specimen
[10:25] an enlarged image of the specimen that is just what magnification is all
[10:29] that is just what magnification is all about
[10:30] about pretty simple and pretty straight
[10:31] pretty simple and pretty straight forward and the most important thing to
[10:34] forward and the most important thing to also take away from this
[10:36] also take away from this is if you want to be able to see
[10:39] is if you want to be able to see something if you want to be able to see
[10:41] something if you want to be able to see something it must have the capability of
[10:45] something it must have the capability of interrupting the light
[10:50] and reflecting the light this will be
[10:52] and reflecting the light this will be important for later
[10:57] and once it interrupts and reflects the
[10:59] and once it interrupts and reflects the light it will then
[11:01] light it will then enter our eyes and therefore we are able
[11:04] enter our eyes and therefore we are able to
[11:05] to comprehend the image that's how we look
[11:08] comprehend the image that's how we look at it
[11:08] at it that's how we look at things on a daily
[11:10] that's how we look at things on a daily basis
[11:12] basis so for the next video what we're going
[11:14] so for the next video what we're going to be looking at is
[11:15] to be looking at is we're going to be seeing the wavelengths
[11:18] we're going to be seeing the wavelengths of a light microscope