hello everyone welcome to the virtual practical class of manoj academy in today's class we are going to see the different parts of a compound microscope and we are also going to talk about how the different parts work now this is a typical compound light microscope why is it called a light microscope it is called a light microscope because we use a source of light to illuminate the specimen that we are trying to see so in this microscope we will use led light however you can also use natural or artificial light to light up or eliminate the specimen why is it called a compound microscope it is known as a compound microscope because in this microscope we use two different lenses with different magnifications so that your final image has a much larger magnification so let us see what are the different parts and how they help in observing specimens so the first part of the microscope that you see here is this region which is known as the foot the foot is the base on which this entire microscope is standing here this arched part is known as the arm and the arm is holding this body to which two types of lenses are attached the first lens that is attached to the body is this lens which is known as the eyepiece lens if you see closely the eyepiece lens has a certain magnification which here is written as 25x you may have an eyepiece lens which is 10x that is magnifies the image 10 times you may also have an eyepiece lens which is 15x which is magnifying an image 15 times at the base of the body we have this rotatable disc which is known as the nose piece the nose piece in this microscope has three lenses attached and these lenses are known as objective lenses if you look closely you will see that all these three lenses have different degrees of magnification mentioned on them the lowest power here is usually 10 times that is 10x and the highest power is usually 40x 45x or 65x here we have three magnifications for the objective lens 10x which is low power 45x which is higher than 10x and 100x which is the highest power in this microscope then you have this stage this metallic stage is the base on which we will keep our specimen and this base has been provided with clips which will help us to hold the slide in position the source of light in this microscope is the led bulb that we are using here however you might have seen a microscope in the laboratory where a mirror is usually used this mirror that we use is a plano concave mirror which means that one side of the mirror is plane that is straight and the other side is concave the concave mirror as you must be knowing is responsible for collecting light from different directions and focusing it to one point so we use this mirror and we attach it here to the base of the microscope so that the mirror can collect light from different directions and send it into the specimen or onto the specimen if you want to adjust the amount of light entering let's say the field the microscopic field is appearing too bright you might want to reduce the amount of light in that case we have a diaphragm here which you can rotate to adjust the amount of light entering and leaving this diaphragm is almost like the iris of your eye so with the iris just like you decrease or increase the diameter of your pupil you can do that same thing with this diaphragm now we have to bring the specimen to the focus of these two lenses you must be aware that if you have a camera with which you're focusing something which is right in front of you you cannot use that same camera to focus something which is far away this i'm talking about the dslr camera so in that case what do you have to do after focusing on the on the object which is near you you can focus on another object which is further away but you have to bring that object into the focus of the camera so similarly here whenever you're putting a specimen on the stage you have to adjust so that the image is at the focus the specimen is at the focus all right so how do we do that for that we have these two screws the first one which is this large one is known as the coarse adjustment screw if you see this one and if you just rotate this one you can clearly see that the body is moving up and down along with the lenses this increases or decreases the gap between the stage and the lens objective lens and that helps in bringing the image in focus now we all have different powers in our natural eye lens if you are if you wear a specks you have a different power i have a different power and that is why even after i focus the object with the help of this coarse adjustment screw it may so happen that it is exactly focused for my eye lens but it is not for yours because you have a different power so in that case you might want to make fine adjustments but you do not want to completely move the body up and down in that case we have this one which is known as the fine adjustment screw with which see if when i am rotating the fine adjustment screw there is no movement of the body so it is basically adjusting the lens very minutely without moving the entire body and with this you can bring the specimen to your own focus right now we will show you a slide so this is a glass slide on which generally we put a specimen which we need to observe under the microscope and so that your specimen does not fly away it does not dry out it is not damaged we usually cover the specimen with a coverslip you can see this is an absolutely fine piece of glass which we use to cover and and save the specimen from being damaged now once you have prepared your slide sometimes we have prepared slides for example we have a large number of prepared slides here i will show you one of them so this slide is off the algae spirogyra as you can see there is a coverslip here in this case the cover slip is round but you may also have square cover slips like this right so this is a permanent slide which has already been prepared and this will stay for a very long time it will not get damaged because it has been preserved that way so now what we'll do is we will take this slide and we will place it on the stage and secure the position of the slide with the help of the clip now with this you have the slide on the stage on the stage there is a small aperture through which the light will enter and it will fall on the specimen that is all right but you might have to move the slide right left forward or backwards for that you have usually this kind of a screw attached to your microscope certain compound microscopes may not have this screw in that case you have to manually move the slide however if you are provided with these screws as you can see we can move the screws and move the slides right and left backwards or forward now once we have brought the slide and the specimen right in the same line as the lenses we can start using the coarse adjustment screw to focus now at this point of time i am using 100x for the objective lens and 25 x for the eyepiece lens so if i'm using 100x and 25x then first the specimen is magnified 100 times and then that 100 times magnified image is magnified another 25 times so yeah you are getting overall a magnification of 2500 times of the actual size of the specimen that you see here so how do we observe it we will have to place our eye on the eyepiece lens and make sure that the mirror is collecting enough light and focusing it on the specimen so when you do that you will see that your entire field that you can see under the microscope is lighted up is illuminated it is not dark it is not black it is illuminate illuminated so when you move the mirror the mirror will be able to collect light from natural sources or artificial sources you can do this in front of a light which is artificial or you can do it in front of a window through which sunlight is coming in right so then you start adjusting your focus by moving the coarse adjustment screw and while you are doing that you can move your slide right or left so that you can bring the specimen right beneath the objective lens and now i can see a very distinct view of the algae spirogyra under my microscope so this is how the specimen looks under the microscope in high power and in low power hope you enjoyed today's session we will come back with more practical classes from manoj academy take care thank you subscribe to our channel and go to our website www.manojaacademy.com for courses on physics chemistry biology mathematics and computer coding hope you will have fun happy learning