Which one of the following is the correct sequence of passage of light in a compound microscope?
Condenser-Objective lens-Body tube-Eyepiece
Understanding the path that light takes as it travels through a compound microscope is fundamental to comprehending how the instrument works to magnify specimens. The light source is usually at the base, and the light travels upwards through various components before reaching the observer's eye.
Let's break down the common components of a compound microscope involved in the passage of light:
- Condenser: This component is located below the stage. Its main function is to focus the light from the source onto the specimen placed on the stage.
- Specimen: The object being viewed is placed on the stage, in the path of the focused light.
- Objective Lens: Located just above the specimen on the revolving nosepiece. This is the first lens the light passes through after the specimen. It produces a magnified, real, and inverted image.
- Body Tube: This is a tube connecting the objective lens to the eyepiece. The light travels through this tube carrying the image formed by the objective lens.
- Eyepiece (Ocular Lens): Located at the top of the body tube where the observer looks. It magnifies the image produced by the objective lens, creating the final, magnified, virtual image that the observer sees.
Correct Sequence of Light Passage in a Compound Microscope
Based on the function and position of these parts, the light typically originates from a source (like a bulb or mirror), passes through the condenser, then the specimen, followed by the objective lens, travels up the body tube, and finally exits through the eyepiece to the observer's eye. Considering the components listed in the options, the sequence of light passage is:
- Condenser
- Objective lens
- Body tube
- Eyepiece
Analyzing the Options for Light Path in Microscope
Let's evaluate the given options based on this correct sequence:
- Option 1: Condenser-Objective, lens-Eye-piece-Body tube. This sequence places the eyepiece before the body tube, which is incorrect as the light travels through the body tube to reach the eyepiece.
- Option 2: Objective, lens-Condenser-Body tube-Eyepiece. This sequence places the objective lens before the condenser, which is incorrect. The condenser focuses light onto the specimen before it reaches the objective lens.
- Option 3: Condenser-Objective lens-Body tube-Eyepiece. This sequence correctly follows the path of light from below the stage (condenser), through the first magnifying lens (objective), along the tube connecting the lenses (body tube), and finally through the second magnifying lens (eyepiece).
- Option 4: Eyepiece-Objective lens-Body tube-Mirror. This sequence starts with the eyepiece and includes the mirror (light source/reflector), which is at the beginning of the path, not towards the end after the lenses and body tube. This is incorrect.
Therefore, the sequence Condenser → Objective lens → Body tube → Eyepiece accurately describes the path of light through the specified optical components of a compound microscope.
Revision Table: Compound Microscope Light Path Components
| Component | Position in Light Path (Sequence) | Main Function |
|---|---|---|
| Condenser | Early (after light source, before specimen) | Focuses light onto the specimen |
| Objective Lens | After specimen, first magnifying lens | Forms magnified, real, inverted image |
| Body Tube | Connects objective lens and eyepiece | Path for light/image |
| Eyepiece | Last magnifying lens (ocular lens) | Magnifies image from objective, forms virtual image |
Additional Information on Compound Microscope Operation
A compound microscope uses two sets of lenses: the objective lens and the eyepiece lens. The objective lens creates an initial magnified image of the specimen. This image is then further magnified by the eyepiece lens. The total magnification of the microscope is the product of the magnification of the objective lens and the magnification of the eyepiece lens.
Total Magnification = \( \text{Magnification of Objective Lens} \times \text{Magnification of Eyepiece} \)
Proper focusing involves adjusting the distance between the objective lens and the specimen (using coarse and fine adjustment knobs) and sometimes adjusting the condenser and diaphragm to control the amount and focus of light reaching the specimen. The light path is crucial for achieving a clear and well-magnified image.
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