IB Biology: A2.2-Measuring Cells

What is the purpose of calibrating the eyepiece graticule?

• To determine the actual length of eyepiece units using a stage micrometer.

• To enhance the brightness of the microscope image.

• To adjust the focus of the microscope lens.

• To measure the temperature of the specimen.

What units are used to measure cells?

• Metres

• Centimetres

• Millimetres

• Nanometres

What is the process to measure a cell in eyepiece units?

• Calibrate the eyepiece units with a stage micrometer to determine the length of one eyepiece unit, then multiply the length of one eyepiece unit by the eyepiece measurement.

• Use a ruler to measure the cell directly under the microscope.

• Estimate the size of the cell based on the magnification of the microscope.

• Count the number of cells in a given area and divide by the area to find the average size.

How is the eyepiece graticule calibrated?

• By superimposing the images of both the eyepiece graticule and stage micrometer and counting the eyepiece units that correspond to 0.1mm.

• By measuring the distance between two known points on the stage micrometer without any superimposition.

• By adjusting the focus of the microscope until the graticule is clear and visible.

• By using a digital caliper to measure the eyepiece units directly.

How do you convert from mm to µm?

• Multiply the length in mm by 1000 to convert to µm.

• Divide the length in mm by 1000 to convert to µm.

• Add 1000 to the length in mm to convert to µm.

• Subtract 1000 from the length in mm to convert to µm.

What are the subdivisions of a stage micrometer?

• 0.1mm and 0.01mm

• 0.5mm and 0.05mm

• 1mm and 0.1mm

• 0.2mm and 0.02mm

What instruments are used to measure cells?

• The eyepiece graticule and stage micrometer

• The microscope and petri dish

• The pipette and test tube

• The spectrophotometer and centrifuge

What is a stage micrometer?

• A type of microscope used for measuring small objects.

• A miniature transparent ruler found on a special glass slide used to calibrate eyepiece units.

• A device for measuring the intensity of light in a microscope.

• A tool used for adjusting the focus of a microscope.

What is an eyepiece graticule?

• A transparent scale placed in the eyepiece of the microscope to measure the length of a cell in eyepiece units.

• A type of lens used to magnify objects in a microscope.

• A device that adjusts the brightness of the microscope's light source.

• A filter used to enhance color contrast in microscopic images.

How many divisions does an eyepiece graticule typically have?

• 50 divisions

• 75 divisions

• 100 divisions

• 150 divisions