Q: If the wavelength of light ($$\lambda) $$used is 550 nm and the numerical aperture (A.N.) of the objective is 1.25, what is the theoretical limit of resolution ($$d) $$for the microscope? Use the formula $$d = \frac{0.5 \lambda}{A.N.}.$$

$$d = \frac{0.5 \times 550}{1.25} = 220 nm$$

Q: Which of the following formulas correctly calculates the resolution ($$d) of a $$light microscope?

$$d = \frac{\lambda}{2 \times A.N.}$$

Question 1

A student is using a compound light microscope with a 10X ocular lens and a 40X objective lens. What is the total magnification being used?

Accepted Answer

$$10 	imes 40 = 400X$$

Question 2

Which of the following best describes the function of immersion oil when using the 100X objective lens on a compound microscope?

Accepted Answer

It increases the numerical aperture by reducing light refraction between the specimen and the lens.

Question 3

If the wavelength of light ($$\lambda) $$used is 550 nm and the numerical aperture (A.N.) of the objective is 1.25, what is the theoretical limit of resolution ($$d) $$for the microscope? Use the formula $$d = \frac{0.5 \lambda}{A.N.}.$$

Accepted Answer

$$d = \frac{0.5 	imes 550}{1.25} = 220 nm$$

Question 4

Which part of the compound microscope is responsible for fine-tuning the focus after the initial coarse adjustment?

Accepted Answer

Micrometric adjustment knob

Question 5

A student observes that when moving the slide to the left, the image appears to move to the right. What property of the compound microscope explains this phenomenon?

Accepted Answer

The image is inverted due to the arrangement of the lenses.

Question 6

Which of the following best distinguishes between magnification and resolution in microscopy?

Accepted Answer

Magnification increases the size of the image, while resolution determines the ability to distinguish two close points as separate.

Question 7

A microbiologist wants to observe the detailed structure of bacterial cell walls. Which objective lens and technique should be used for the best resolution?

Accepted Answer

100X oil immersion objective with immersion oil

Question 8

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

Accepted Answer

The resolving power increases (the value of $$d$$ decreases).

Question 9

Which of the following formulas correctly calculates the resolution ($$d) of a $$light microscope?

Accepted Answer

$$d = \frac{\lambda}{2 	imes A.N.}$$

Question 10

A student is using a 10X ocular and a 100X oil immersion objective. The field of view appears very dim. What is the most appropriate adjustment to improve brightness without losing resolution?

Accepted Answer

Increase the intensity of the light source.

Question 11

Which bacterial arrangement is described as spherical cells in chains?

Accepted Answer

Streptococci

Question 12

Why is it important to clean the objective and ocular lenses with lens paper before and after using the microscope?

Accepted Answer

To prevent scratches and remove residues that can distort the image.

Question 13

A student calculates the total magnification as 1,000X using a 10X ocular and a 100X objective. If the field of view at 100X total magnification is 2 mm, what is the approximate field of view at 1,000X?

Accepted Answer

0.2 mm

Question 14

Which of the following is NOT a correct safety practice when handling a compound microscope?

Accepted Answer

Carrying the microscope by the ocular lens.

Question 15

A sample is being observed under the 100X oil immersion objective, but the image is blurry. Which of the following is the best first step to improve focus?

Accepted Answer

Use the micrometric (fine) adjustment knob.

Question 16

Which of the following best explains why immersion oil improves resolution when using the 100X objective?

Accepted Answer

It has a refractive index similar to glass, reducing light refraction and increasing the amount of light entering the lens.

Question 17

If a bacterium is 1.5 micrometers in length, and the microscope's resolution limit is 0.2 micrometers, will the bacterium be visible as a distinct object? Why?

Accepted Answer

Yes, because its size is greater than the resolution limit.

Question 18

Which of the following best describes the function of the condenser in a compound microscope?

Accepted Answer

It concentrates light onto the specimen to improve illumination.

Question 19

A student is observing a slide with a mixture of cocci and bacilli. Which of the following best describes the difference in their morphology?

Accepted Answer

Cocci are spherical, while bacilli are rod-shaped.

Question 20

Which adjustment should be made first when focusing a specimen under the microscope?

Accepted Answer

Use the macrometric (coarse) adjustment knob with the lowest power objective.

Microscopio Compuesto de Campo Claro y Morfología de Bacterias: Fundamentos para Biología y Bioquímica

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