Question

Place the counting chamber on the microscope and locate the grid in the center, using the low-power objective lens. Do not increase the magnification until you have found the grid on low power. (Hint: Close the iris diaphragm to bring the grid lines into view. Too much light will make them impossible to see.) Increase the magnification, focusing one objective at a time, until you have the cells and the grid in focus with the oil immersion lens. (In some cases, high dry is sufficient.)

Short answer

Place the chamber, find the grid at low power, adjust light, increase magnification, and focus using the oil immersion lens.

Step-by-step solution

Place the Counting Chamber

Put the counting chamber on the microscope stage securely.

Locate the Grid at Low Power

Use the low-power objective lens to find the grid in the center. This helps in initially locating the grid lines.

Adjust Light Source

Close the iris diaphragm to reduce the light. This will help make the grid lines visible, as too much light can obscure them.

Increase Magnification

Once the grid is visible, slowly increase the magnification. Focus one objective at a time, gradually moving to higher power lenses.

Focus with Oil Immersion Lens

Continue to focus until you have both the cells and the grid in view using the oil immersion lens. In some cases, using the high dry lens might be sufficient.

Key concepts

counting chamber placement

The counting chamber, also known as a hemocytometer, is a specialized slide used for cell counting. First, ensure the counting chamber is clean and dry.
Place the counting chamber securely on the microscope stage.
Align the chamber so that it is stable and will not move while you manipulate the microscope settings.
This initial placement is crucial as it will directly affect the quality of your observations.
Securing it properly will prevent it from slipping or going out of focus when you switch between different lenses or adjust the stage.

low-power objective lens

The low-power objective lens is typically 10x magnification and is used to locate the specimen on the slide.
Rotate the nosepiece to position the low-power objective lens directly over the counting chamber.
Look through the eyepiece and use the coarse focus knob to bring the grid into clear view.
Finding the grid at low power is essential before moving to higher magnifications.
Using low power first allows you to get an overall view and locate the specific area of interest easily.

iris diaphragm adjustment

The iris diaphragm controls the amount of light that reaches the specimen. Too much light can wash out the details, whereas too little can make it hard to see anything.
Locate the iris diaphragm control, often found beneath the stage or integrated with the condenser.
Close the iris diaphragm slightly to decrease the light intensity, making the grid lines more visible.
Adjusting the iris diaphragm properly helps in improving the contrast and details of the grid and cells.

oil immersion lens

The oil immersion lens, usually 100x magnification, provides the highest level of detail.
Once you've progressively moved through lower magnifications and located the grid, apply a tiny drop of immersion oil directly onto the grid area.
Carefully rotate the oil immersion lens into place without touching the slide with the lens.
Use the fine focus knob to bring the cells and grid lines into sharp focus.
Oil immersion effectively increases the resolution by reducing light refraction, allowing you to see tiny details clearly.

high dry lens

The high dry lens, usually 40x magnification, can sometimes be enough for certain observations.
Switch to the high dry lens if the oil immersion lens is not required.
Focus the lens while keeping the iris diaphragm slightly more open than you would for the oil immersion to allow more light.
High dry lenses are useful for quickly scanning larger areas or when less detail is needed.
They offer a good balance between magnification and ease of use, without the need for oil.