Q: What is the correct formula for calculating the resolving power of a microscope?

$$\text{Resolving power} = \frac{\text{wavelength}}{2 \times \text{numerical aperture}}$$

Question 1

Which part of the compound microscope is responsible for focusing light through the specimen and is adjusted to optimize illumination?

Accepted Answer

Condenser

Question 2

A student is observing bacteria under a microscope. Which objective lens and technique should they use to achieve the highest resolving power?

Accepted Answer

100× oil immersion objective with immersion oil

Question 3

What is the total magnification when using a 40× objective lens and a 10× ocular lens?

Accepted Answer

$$10 	imes 40 = 400$$

Question 4

Why is immersion oil used with the 100× objective lens but not with the 40× objective lens?

Accepted Answer

Immersion oil increases numerical aperture and matches the refractive index of glass, reducing light refraction and improving resolution at high magnification.

Question 5

A field of vision at 10× objective is 2 mm. If a yeast cell is 10 μm long, how many yeast cells can fit end-to-end across the field?

Accepted Answer

$$\frac{2000\ \mu m}{10\ \mu m} = 200$$

Question 6

Which bacterial morphology is described as rod-shaped and can occur singly, in pairs, or in chains?

Accepted Answer

Bacillus (bacilli)

Question 7

What is the correct formula for calculating the resolving power of a microscope?

Accepted Answer

$$	ext{Resolving power} = \frac{	ext{wavelength}}{2 	imes 	ext{numerical aperture}}$$

Question 8

A student accidentally rotates the 40× objective through immersion oil. What is the correct action to take?

Accepted Answer

Wipe the 40× objective immediately with lens paper and inform the instructor.

Question 9

Which of the following best explains why the field of vision decreases as magnification increases?

Accepted Answer

Higher magnification lenses have a smaller field diameter, allowing you to see a smaller area in greater detail.

Question 10

Which of the following is NOT a correct rule for using the microscope?

Accepted Answer

Use Kimwipes to clean the lenses.

Question 11

A student observes a cluster of spherical bacteria under oil immersion. What is the most likely arrangement and morphology?

Accepted Answer

Staphylococcus (cocci in clusters)

Question 12

If the numerical aperture (N.A.) of a lens is increased, what is the effect on resolving power, assuming wavelength remains constant?

Accepted Answer

Resolving power improves (distance decreases)

Question 13

Which of the following organisms would most likely require the use of the high-dry (40-45×) objective for optimal observation?

Accepted Answer

Algae

Question 14

A student is using a compound microscope with a 10× ocular and a 100× oil immersion objective. The field diameter at 10× is 2 mm. What is the approximate field diameter at 100×?

Accepted Answer

$$\frac{2\ mm}{10} = 0.2\ mm$$

Question 15

Which of the following best describes the function of the iris diaphragm?

Accepted Answer

It controls the cone of light and adjusts contrast versus brightness.

Question 16

Which of the following is a correct step when switching from low power to oil immersion objective?

Accepted Answer

Swing the 40× objective out of the light path before adding oil.

Question 17

Which of the following statements about numerical aperture (N.A.) is correct?

Accepted Answer

A higher N.A. allows the lens to gather more light and resolve finer detail.

Question 18

A student observes a flexible, helical-shaped bacterium under oil immersion. Which morphology is this?

Accepted Answer

Spirochete

Question 19

Which of the following is the best reason for starting with the low power objective when viewing a new slide?

Accepted Answer

It provides a larger field of vision, making it easier to locate and center the specimen.

Question 20

After using the oil immersion lens, what is the correct procedure before storing the microscope?

Accepted Answer

Wipe oil off the objective with lens paper and return the microscope with a dust cover.

LAB 1: Microscopy in Microbiology: Use, Care, and Observation of Microorganisms

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