Comprehensive Guide to Parts of a Compound Microscope (Class 11)

Introduction

The first compound microscope was invented by Z. Janssen. Since Janssen was a teenager, his father Hans supported him in both his writing and the creation of the first microscope. They found a compound microscope with two lenses, one lens placed close to the object and the other serving as the eyepiece. Through a compound microscope, people can view the samples or specimens with high magnification. This experiment deals with different parts of the compound microscope(mechanical parts and optical parts).

Table of Contents

1. Aim

2. Apparatus required

3. Theory 

4. Procedure

5. Observations 

6. Result

7. Precautions

8. Lab Manual Questions 

9. Viva Questions 

10. Practical Based Questions 

11. Conclusion

12. FAQs

Aim

To study parts of a compound microscope

Apparatus Required

• A compound microscope

• Silk cloth

• Lens cleaning fluid 

• Lens cleaning paper

• Notebook 

Theory

What is a Compound Microscope?

An instrument called a compound microscope has a combination of lenses that are used to view enlarged images of tiny objects that are placed on a glass slide. A combination of lenses can produce accurate and enlarged images of tiny particles or things. Compared to other low-power microscopes, a compound microscope has the ability to attain higher magnification levels.

Parts of Compound Microscope

Parts of a Compound Microscope

The several parts of a compound microscope are classified into two major categories, 

1. Mechanical Parts

2. Optical Parts

A. Mechanical Parts

• A base: It is the foot of the microscope that bears all of the weight of the microscope.

• Pillar: It supports the stage of the microscope by resting on the base.

• Arm: It is a curved structure. The entire microscope can be handled using this arm. 

• Stage: The stage is the flat plate that is attached to the lower part of the arm. The specimen is set up on the stage for observation and examination. There is a hole in the middle of the stage through which light can enter.

• Inclination joint: It is a joint where the arm is attached to the pillar of the compound microscope. This joint can be used to tilt the microscope.

• Clips: Two clips are connected to the upper portion of the stage. With the help of these clips, the slide can be kept in place.

• Diaphragm: The diaphragm is fixed in place below the stage. It regulates and modifies the amount of light that enters the microscope. 

• Nose Piece: The bottom end of the body tube is joined to the revolving, circular nose piece. The nose piece has three holes wherein the objective lenses are inserted.

• Body tube: It is a hollow and tubular structure, and is part of the arm's top portion on the microscope. It is possible to control the body tube with the help of adjustment knobs.

• Fine adjustment knob: It is a smaller knob used to focus an object precisely and sharply. 

• Coarse Adjustment knob: It is a large knob used to adjust the body tube to precisely focus on the specimen.

B. Optical Part

• Eyepiece lens: It is also known as ocular. It is mounted at the top of the body tube. There are several markings, such as 5X, 10X, 15X, etc., on the eyepiece's rim. These show the magnification strength. With the help of this eyepiece, the object's magnified image can be observed.

• Mirror: The mirror is located above the base. It is used to reflect light into the microscope. On one side is a regular mirror, and on the other is a concave mirror.

• Objective lenses: There are two objective lenses attached to the rotating nosepiece at the base of the body tube. These three lenses are, the oil immersion objective lens – 100X, high power objective lens – 45X, and low power objective lens – 10X.

Working of a Compound Microscope

1. A compound microscope uses a combination of lenses to improve the magnification and resolving power while observing the specimen. 

2. The specimen or object to be examined is mounted on a transparent glass slide and positioned on the specimen stage between the condenser and objective lenses.

3. A beam of visible light from the base is focused on the specimen by a condenser lens.

4. The specimen's light is captured by the objective lens, which magnifies it inside the body tube to create the primary image. This image is once more magnified by the ocular lens or eyepiece.

5. In order to line the higher magnification objective (often 45X) with the lighted portion of the slide is used. The compound microscope's nosepiece must be turned after low-power focusing.

6. Sometimes it is necessary to use a very high magnification (e.g. for observing bacterial cells). In this case, an oil immersion objective lens (typically 100X) is used.

Procedure

1. Look through the eyepiece and adjust the mirror so that enough light can enter the microscope.

2. The slides, stage, mirror, and lenses all need to be dust-free and clean.

3. The centre of the stage should have a slide.

4. To ensure that the slide cannot move, firmly fasten clips to both of its edges.

5. The low power objective is aligned with the focal point that has been placed on the slide by adjusting the nose piece.

6. You can move the coarse adjustment knob upwards or lower until the slide is clearly in focus.

7. To get a clean and sharp image of the object in focus, move the fine adjustment knob upwards or downwards.

8. Under a low power objective, all of the object's fine details can be seen. Students can sketch the diagram of whatever they observe.

9. The high power objective is now aligned with the object by turning the nosepiece. To obtain a clear and accurate image of the object, the fine adjustment knob can be set as required.

10. The features of the object can be seen at high magnification. 

11. Draw all the necessary diagrams of your observations.

12. When the object is being studied with high power, the coarse adjustment knob shouldn't be used since it could break the slide.

Observations

• The microscope has a sturdy base foot, and its vertical arm and inclination joint are linked together. For more easy use, the arm can be tilted at various angles.

• The microscope's stage is square, rectangular, or spherical, and the arm is fixed. A tiny hole in the middle of the stage is circular.

• Two clips or other mechanical devices are supplied on the stage for fixing and retaining the slide securely in place. 

• Below the condenser is a fitting mirror that may be adjusted. It has plano-concave surfaces to concentrate the rays of light.

• A moveable tubular body tube serves as the microscope's body.

• The tube has an eye or ocular.

• A particular component of magnification that can be adjusted for lower or higher

• magnifying power, such as 5X, 10X, or 15X. 

• Additionally, eyepieces with pointers are also available.

• A pair of objective lenses (10X, 40X, or 45X) are mounted at the bottom end of the nosepiece. 

• A third objective lens (100X) known as an oil immersion lens may also be present in some microscopes.

• With the use of the coarse adjustment knob and the fine adjustment knob, the tube containing the eye and objective lenses can be raised or lowered to sharply focus the object.

• The coarse adjustment is used to examine the object at lesser magnification first, and the rotating nosepiece with the fixed objective lenses is used to view it at higher magnification.

• Only the fine adjustment knob is used for fine focus setting while viewing at higher magnification.

Result

All the parts of the compound microscope were observed and studied.

Precautions

1. Handle the microscope with both hands.

2. Before using, the objective lenses and eyepiece should be cleaned with a silk cloth and cleaning solution.

3. When using the microscope, it should not be tilted.

4. When examining an object, start with a low power objective and work your way up to high power.

5. After all observations have been made, the lower power must remain in place.

6. It is important to focus carefully so that the objective lens never comes in contact with the stage or the slide.

7. When using the high power objective, you should only use the fine adjustment knob.

8. Before observing a specimen in a microscope make sure that the well-mount preparations are covered with a cover slip.

9. Use the concave portion of the mirror in low light.

10. Without oil, oil immersion lenses should never be used.

Lab Manual Questions

1. What is the magnification achieved when a 15X eyepiece and a 40X objective are used together?

Ans:Microscope lenses are eyepiece (situated near eye) and objective lens(situated near the sample).Magnification is calculated by multiples of power of eyepiece and power of objective lens.Magnification of 15X and 40X is 600X.

2. What would happen if direct sun rays are focused by the mirror into the body tube?

Ans:When sun rays are focused by the mirror into the body tube, magnified images of the specimen can be seen.But sunlight is harmful to human eyes.

3. What is the difference between a dissecting and a compound microscope?

Ans:Dissecting microscope has magnification upto 70X and compound microscope has magnification from 400X to 1000X.

4. To which part of a microscope are the objective lenses fitted? 

Ans:Objective lenses are located to the rotating nose piece.They are used to magnify the image of specimens.

Viva Questions

1. What are the different types of microscopes known?

Ans: Simple microscope,compound microscope,electron microscope,

Stereo microscopes are different types of microscopes.

2. Which lens is used in the compound microscope?

Ans: Compound microscope uses two convex lenses. One is the eyepiece or ocular lens and the other is an objective lens.

3. What magnification does the microscope need to see bacteria?

Ans: Bacteria are microorganisms (small organisms).1000X magnification can view the bacteria .

4. What type of microscope is most used in science classes?

Ans: Stereomicroscope, compound microscope is most used microscopes in science classes.

5. Why do we need to start with the lowest magnification setting when using a microscope?

Ans: When we use a compound microscope we start with lower magnification as it allows us to focus our specimen and the cells.

6. What is the use of a compound microscope?

Ans: Compound microscope has high magnification.Study of bacteria made easy through compound microscope.

7. What is base in a compound microscope?

Ans: Bottom of the microscope that supports the microscope.Illuminator is located at the base of the microscope.

8. Who invented the compound microscope?

Ans: Hans and Zacharis Janssen invented compound microscopes in the late sixteenth century.

9. Who is the father of the microscope?

Ans: Antonie van leeuwenhoek is the father of microscope.He observed bacteria, vacuole of the cell.

10. What are the parts of a compound microscope?

Ans: There are three parts of a compound microscope. They are the head, base, and arm(connects the base and head of the microscope).

Practical-Based Questions 

1. The magnifying power of the compound microscope is the product of the magnification of the objective lens and _____.

1. Eyepiece

2. Arm

3. Reflector

4. Body tube

Answer: A. Eyepiece

2. The use of a single convex lens or groups of lenses is found in _____.

1. Telescopes

2. Fluorescent lamps

3. Magnifying glass

4. Option A and C.

Answer: D. Option A and C.

3.  _____ is the metallic platform that is fitted to the lower part of the arm with a hole in the centre.

1. Base

2. Drawer tube

3. Stage

4. Automatic Stop

Answer: C. Stage

4. The stereo microscope provides

1. Single-dimensional picture

2. Image in two dimensions

3. Image in three dimensions

4. None of the options

Answer: C. Image in three dimensions

5. The ____ can be changed to focus the light.

1. Condenser 

2. Base 

3. Stage 

4. Automatic Stop

Answer: A. Condenser

6. How much magnification does the eye's lens offer?

1. 2x 

2. 3x 

3. 15x 

4. 50x

Answer:  C. 15x.

7. The _______focuses the image under low power.

1. Revolving nosepiece

2. Fine adjustment knob

3. Coarse adjustment knob

4. Arm/neck

Answer: C. Coarse adjustment knob

8. The__________ sharpens the image under high magnification.

1. The diaphragm

2. Fine adjustment knob

3. Coarse adjustment knob

4. The ocular

Answer: B. Fine adjustment knob

9. A light microscope that has more than one lens, the ocular and objective lens, is called a _______________.

1. Compound microscope

2. Microscope

3. Electrical microscope

4. Telescope

Answer: A. Compound microscope

10. The higher the magnification, the ________ you see of the specimen.

1. More

2. Less

3. Higher

4. Lower

Answer: B. Less

Conclusion

One of the common microscopes that are widely used for the observation of specimens is the compound microscope. It has a combination of lenses. The compound microscope is mostly used to examine the structural specifics of individual cells, tissues, or organ parts. Compound microscope components can be divided into two categories:

Mechanical and optical parts. The mechanical parts include a base, pillar, arm, stage, inclination joint, clips, diaphragm, nose piece, body tube, fine adjustment knob and a coarse adjustment knob. The optical part includes an eyepiece lens, mirrors and objective lenses. This topic has provided all the information regarding parts of a compound microscope in detail.