HTL Laboratory Instrumentation & Equipment 3 — Questions and Answers
Question 1: The numerical aperture (NA) of an objective lens directly determines the microscope's:
- Working distance
- Resolving power (Correct answer)
- Magnification factor
- Depth of field only
Correct answer: Resolving power
Numerical aperture determines the resolution of the objective; higher NA allows finer detail to be distinguished.
Question 2: Paraffin sections that consistently fold or wrinkle as they come off the microtome knife are MOST likely caused by:
- Too slow a cutting speed
- Block temperature that is too warm (Correct answer)
- Insufficient section thickness
- High ambient humidity
Correct answer: Block temperature that is too warm
A warm paraffin block is too soft to hold its shape, causing sections to fold and wrinkle as they are cut.
Question 3: Which staining instrument component directly controls the volume of reagent dispensed onto each slide in an autostainer?
- Peristaltic pump (Correct answer)
- Solenoid valve
- Heating element
- Agitation arm
Correct answer: Peristaltic pump
Peristaltic pumps deliver precise, reproducible volumes of reagents to slides in automated staining platforms.
Question 4: A laboratory centrifuge showing excessive vibration during operation should FIRST be evaluated for:
- Motor brush wear
- Imbalanced rotor load (Correct answer)
- Lid gasket failure
- Incorrect speed setting
Correct answer: Imbalanced rotor load
Imbalanced loading of the rotor is the most common cause of centrifuge vibration and must be corrected to prevent damage and injury.
Question 5: Köhler illumination is set up on a brightfield microscope primarily to:
- Maximize depth of field
- Provide even, glare-free illumination and optimize resolution (Correct answer)
- Increase working distance
- Enable dark-field imaging
Correct answer: Provide even, glare-free illumination and optimize resolution
Köhler illumination ensures uniform, focused light across the entire field of view while minimizing glare and maximizing resolution.
Question 6: Which type of coverslipping machine uses a solvent-based mounting medium applied in a continuous film process?
- Manual coverslipper
- Aqueous wet coverslipper
- Automated linear coverslipper (Correct answer)
- Heat-seal coverslipper
Correct answer: Automated linear coverslipper
Automated linear coverslippers dispense solvent-based media continuously and apply coverslips in-line with slide transport.
Question 7: When a tissue processor cycle is interrupted mid-run due to a power failure, the safest immediate action is to:
- Manually advance all tissues to the next station
- Leave tissues in the current reagent until power is restored
- Transfer all tissues to 70% ethanol
- Complete the remaining steps manually following the processor protocol (Correct answer)
Correct answer: Complete the remaining steps manually following the processor protocol
Manually completing the remaining protocol steps ensures tissues are properly processed without over-fixation or under-dehydration.
HTL Laboratory Instrumentation & Equipment 3
The numerical aperture (NA) of an objective lens directly determines the microscope's: