Exam 3: Observing Microorganisms Through a Microscope

A student is looking at a bacterial specimen using the oil immersion lens, but has forgotten to put immersion oil on the slide. The specimen will appear

Which microscope takes advantage of differences in the refractive indexes of cell structures?

The capsules and flagella of bacteria can be observed in gram -stained smears.

If acid-fast bacteria are stained with the Gram stain, they will stain gram-negative.

Which of the following is NOT true regarding the acid-fast stain?

The resolution of a microscope can be improved by changing the

You are performing a Gram stain on gram-negative bacteria and you stop after the decolorizer step. What is the appearance of the bacteria at this point?

In microscopy, the term resolution

What is the total magnification of a specimen viewed with a 10x ocular lens and a 45x objective lens?

The greater resolution of the electron microscope compared to the compound microscope is due to the longer wavelengths of the electrons used to examine specimens.

You are performing a Gram stain on gram-negative bacteria and you stop after the addition of the mordant. What is the appearance of the bacteria at this point?

You are working in a clinical laboratory and you need to examine an unstained urine sample for the presence of bacteria. What type of light microscope should you use to observe this specimen? Explain your answer.

Which of the following pairs is mismatched?

The purpose of the ocular lens is to

Which microscope is used to observe viruses and the internal structure of thinly sectioned cells?

The limit of resolution of the compound microscope illuminated with visible light is approximately 0.2 μm.

In using this microscope, the observer does NOT look directly at an image through a lens.

This microscope produces an image of a light cell against a dark background; internal structures are NOT visible.

You are performing a Gram stain on gram-positive bacteria and you stop after the addition of the first dye. What is the appearance of the bacteria at this point?

Which of the following places the steps in the correct sequence? 1- Staining 2- Making a smear 3-Fixing