Microscope is a laboratory instrument that is used to see an enlarged image of a small object which reveals the microscopic properties of that object which are not possible to see with a naked eye.
The most common type of microscope is the Optical microscope also known as the Light microscope which uses the light focused through the lenses on the object to form an enlarged image. An optical microscope can be classified into two i.e., Simple microscope and Compound microscope.
Other types of microscopes used are Polarized microscope, Electron microscopes, Fluorescence microscope, Stereo-microscope, etc.
What is a Simple microscope?
A simple microscope is similar to a magnifying glass that uses a double convex lenses to form an erect and enlarged image of an object when placed within its focal length.
The image formed is virtual which means that the formed image cannot be projected on a screen.
The first convex lens was invented by a Dutch person namely Antoine Van Leeuwenhoek in the 17th century and was also the first microscope ever created. The first simple microscope invented by him consisted of small single high powered converging lens to examine the small organisms of freshwater.
Principle of Simple Microscope
A simple microscope works on the principle that when a tiny object is placed within the focus, a virtual, erect, and enlarged image is formed at the least distance of distinct vision from the eye held close to the lens.
Instrumentation of Simple microscope
The simple microscope includes mechanical as well as optical parts which include:-
- Base: It is the support of the microscope.
- Eyepiece: It is the lens that is used to form an enlarged image of the object. The magnification of the lens varies from 10x to 15x.
- Metal Stand: It provides support and stability to the microscope. It includes a base plate and a vertical rod which is fitted to it.
- Tube: The tube is used to connect the eye piece to the objective lenses.
- Nose piece: It is used to hold other objective lenses which are able to rotate while examination of an object.
- Objective lens: These lenses have a magnification of 10x, 40x, and 100x which can be rotated during the examination and are connected to the nosepiece.
- Stage: A place where the glass slides having samples are placed for examination.
- Stage clips: The clips here are used to properly hold the glass slides.
- Coarse adjustment knob: It is used to focus on scanning.
- Fine adjustment knob: It is used for focusing on oil.
- Diaphragm: It is used to control the amount of light that passes through the stage.
- Condenser: It is used for focusing the light on the sample and have a better view of the enlarged image of sample.
- Mirror: It is placed above the stage with the help of a frame and helps in focusing the surrounding light on the object to be observed.
Working of Simple microscope
A biconvex lens is used in the simple microscope and is manly used to obtain small magnifications such as magnification of fungi, algae, biological materials, fibres, etc.
When the glass slide with the sample is kept on the stage, the light from the light source passes through it. The biconvex lens used in the microscope magnifies the image of the object to provide an enlarged and clear image to view the microscopic features of the sample. The image is then viewed from the other side.
Magnification of Simple microscope
The magnification power of a simple microscope is given as:
M = 1 + D/F
where, M = Magnification of Simple microscope
D = least distance of the distinct vision
F = Focal length of convex lens
Explanation of Ray diagram of Simple microscope
- The object AB is placed between the principal focus F1 and the Optical center O of the convex lens.
- Now a ray of light parallel to the principal axis travels towards the convex lens from the point A and is refracted through the principal focus F2 of the convex lens.
- Another ray of light from the A travels through the Optical center O of the convex lens and passes through the lens along the straight line.
- Now examining both the rays, we can say that both the rays are diverging and will not meet at any point forward. When produced backwards they meet at point A1 where we get the image A1B1.
- The image formed is erect, virtual and magnified.
Applications of Simple microscope
- Used to study soil.
- Used to study the skin diseases by a dermatologist.
- Used to study biological specimens such as Hair, Blood, Skin, Nails, Semen, etc.
- Used in microbiology to study about small organisms such as Fungi, Algae, Diatoms, etc.
- Used in magnification of small parts of different objects such as small parts of watch, mobiles, etc.
- Used in magnification of jewelry items.
- Used in studying the microscopic features of Fibres.
- Used to isolate, identify and compare the forensic samples in crime scene investigations.