Microscopy Practical Quiz

Why must an eyepiece graticule be calibrated for each objective lens?

• Because the eyepiece graticule is an arbitrary scale whose value changes with magnification.

• Because the stage micrometer changes size when magnification is altered.

• Because the light intensity affects the markings on the graticule.

• Because the eyepiece graticule can be damaged by high power.

What is the primary function of a stage micrometer?

• To hold the specimen slide firmly in place.

• To provide a scale with known, real-world units for calibration.

• To measure the magnification of the objective lens.

• To focus the light onto the specimen.

If a student switches from a low-power objective lens to a high-power objective lens, what will happen to the value of one eyepiece unit (epu) in µm?

• It will increase.

• It will decrease.

• It will stay exactly the same.

• It will become zero.

A student observes that 40 units on their eyepiece graticule (epu) line up perfectly with 0.1 mm on the stage micrometer. What is the value of one eyepiece unit in micrometres (µm)?

• 0.4 µm

• 4.0 µm

• 2.5 µm

• 25 µm

What is the correct formula for calculating the actual size of a specimen?

• Actual Size (µm) = Measurement (epu) ÷ Calibration Factor (µm per epu)

• Actual Size (µm) = Calibration Factor (µm per epu) ÷ Measurement (epu)

• Actual Size (µm) = Measurement (epu) × Calibration Factor (µm per epu)

• Actual Size (µm) = Measurement (epu) + Calibration Factor (µm per epu)

A student measures an onion cell to be 25 epu long. Their personal calibration factor for the objective lens being used is 4 µm/epu. What is the actual length of the cell?

• 6.25 µm

• 29 µm

• 100 µm

• 0.16 µm

During the practical, why is it important to measure several different cells and calculate a mean?

• To account for natural biological variation between the cells.

• To ensure the microscope is working correctly.

• To practice the calculation multiple times.

• To use up the entire lesson time.

When setting up for calibration, what is the crucial first step after placing the stage micrometer on the stage?

• Immediately align the '0' marks of both scales.

• Rotate the eyepiece to make the two scales parallel.

• Switch to the highest power objective lens.

• Add a drop of immersion oil to the slide.

According to the lesson plan, what is a simple way to identify which scale is the eyepiece graticule if you are confused?

• The one that is brighter.

• The one with more divisions.

• The one that moves when you turn the eyepiece.

• The one that moves when you move the slide.

A student has calibrated their eyepiece graticule for the low-power objective. What must they do before they can use the high-power objective to measure a specimen?

• Use the same calibration factor as the low-power lens.

• Recalculate the calibration factor using the high-power lens and the stage micrometer.

• Multiply the low-power calibration factor by the difference in magnification.

• Divide the low-power calibration factor by 10.