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I. Proper Installation

Before using the microscope, first install the eyepiece and objective lens. Installing the eyepiece is relatively simple; the key challenge lies in mounting the objective lens. As objective lenses are valuable, improper alignment of the threads during installation may cause them to fall to the ground and break. To ensure safety, students must be instructed to support the objective lens with the index and middle fingers of their left hand while screwing it in with their right hand. This way, even if the lens is not properly attached, it will not drop.

II. Correct Light Adjustment

Light adjustment is a crucial step in microscope use. Some students randomly rotate an objective lens to align with the light aperture instead of using the low-power lens as required. They also tend to adjust the reflecting mirror with one hand, often knocking it loose. Teachers must emphasize the following:

Always use the low-power lens for light adjustment.

Use a small aperture and plane mirror for strong light; a large aperture and concave mirror for weak light.

Adjust the reflecting mirror with both hands until a uniform, bright circular field of view is achieved.

Do not move the microscope after adjusting the light, as this may misalign the light path through the reflecting mirror and aperture.

III. Proper Use of Focus Knobs

Adjusting the focus knobs to locate the specimen is one of the most important yet challenging steps for students. Common mistakes include:

Focusing directly with the high-power lens.

Staring through the eyepiece while raising or lowering the lens tube.

Exceeding the critical object distance (continuing to adjust beyond 2–3 cm) and rotating the focus knobs too quickly.

The first two mistakes can cause the objective lens to collide with the slide, damaging both the slide and the lens. To address these issues, teachers must instruct students to:

Always focus with the low-power lens first.

Slowly lower the lens tube using the coarse focus knob until the objective lens is close to the slide (watch the lens from the side to avoid contact).

Look through the eyepiece with the left eye and gradually raise the lens tube by rotating the coarse focus knob in the opposite direction until the specimen comes into view.

Note that the standard object distance for most microscopes is approximately 1 cm. If no specimen is visible beyond this distance, reposition the slide and repeat the steps.

Use the fine focus knob to sharpen blurry images, narrowing the search range and improving efficiency.

IV. Objective Lens Conversion

When switching from the low-power to the high-power lens, students often push the objective lens directly with their fingers for convenience. However, this can skew the lens’s optical axis, as the revolver is made of soft, high-precision material that may loosen or break if the threads are stressed unevenly. Teachers should guide students to rotate the lower plate of the revolver to switch lenses.

V. Proper Eye Usage

When observing specimens, students should keep both eyes open, focusing through the eyepiece with the left eye. Many students, however, cover or close their right eye, which causes eye fatigue and prevents simultaneous observation and drawing. Teachers should:

Demonstrate the correct technique: keep the left eye close to the eyepiece and attempt to focus the right eye on the field of view.

Recommend practice exercises: hold a piece of paper or hand vertically between the eyes (near the nose) to block mutual vision, then consciously alternate focusing on the left and right sides 3–5 times, morning and evening. Proficiency is typically achieved within a week.

Incorrect microscope operation is common in biology experiments. With careful guidance, conscious correction, and consistent practice, students can master proper and skilled use of microscopes.