Q: What is the correct formula for calculating the resolution of a light microscope?

$$\text{resolution} = \frac{0.61 \lambda}{n \sin \theta}$$

Q: Which of the following statements about numerical aperture (NA) is correct?

NA is defined as $$n \sin \theta$$, where $$n is $$the refractive index and $$\theta is $$half the angular width of the cone of light

Q: If the wavelength of light ($$\lambda) $$used is 0.53 µm, the refractive index ($$n) is 1.0$$, and $$\sin \theta = 0.9$$, what is the theoretical resolution limit of the microscope?

$$\frac{0.61 \times 0.53}{1.0 \times 0.9} = 0.36$$ µm

Question 1

Which component of the light microscope is primarily responsible for determining the resolving power of the instrument?

Accepted Answer

The objective lens

Question 2

A student observes two particles under a microscope. The particles are 0.3 µm apart, but the microscope has a resolution of 0.5 µm. What will the student see?

Accepted Answer

A single blurred point

Question 3

What is the correct formula for calculating the resolution of a light microscope?

Accepted Answer

$$	ext{resolution} = \frac{0.61 \lambda}{n \sin 	heta}$$

Question 4

Why should you only use the coarse adjustment knob with the 4X objective lens and not with higher magnifications?

Accepted Answer

It prevents damage to the slide and objective lens due to the shorter working distance at higher magnifications

Question 5

If you are using a 10X ocular lens and a 40X objective lens, what is the total magnification?

Accepted Answer

$$10 	imes 40 = 400$$

Question 6

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

Accepted Answer

It projects a cone of light onto the specimen to improve illumination

Question 7

A student stains cheek cells with methylene blue and observes them under the microscope. Which structures are most likely to be visible?

Accepted Answer

Cell membrane, nucleus, and cytoplasm

Question 8

What is the main reason for cleaning the slide and coverslip with lens paper before observation?

Accepted Answer

To avoid scratching the glass and to remove dust or oil that could obscure the image

Question 9

Which of the following statements about numerical aperture (NA) is correct?

Accepted Answer

NA is defined as $$n \sin 	heta$$, where $$n is $$the refractive index and $$	heta is $$half the angular width of the cone of light

Question 10

A student switches from the 10X to the 40X objective lens but forgets to re-center the specimen. What is the most likely outcome?

Accepted Answer

The specimen may move out of the field of view due to the smaller field at higher magnification

Question 11

Why is it important to adjust the interpupillary distance when using a binocular microscope?

Accepted Answer

To ensure both eyes see a single, merged field of view for comfortable and accurate observation

Question 12

Which of the following best explains why high magnification with low resolution is not useful in microscopy?

Accepted Answer

It produces a larger but blurry image with little detail

Question 13

If the wavelength of light ($$\lambda) $$used is 0.53 µm, the refractive index ($$n) is 1.0$$, and $$\sin 	heta = 0.9$$, what is the theoretical resolution limit of the microscope?

Accepted Answer

$$\frac{0.61 	imes 0.53}{1.0 	imes 0.9} = 0.36$$ µm

Question 14

Which step should be performed LAST when preparing a cheek cell slide for observation under the microscope?

Accepted Answer

Observing the slide under low power

Question 15

What is the main function of the iris diaphragm in a light microscope?

Accepted Answer

To adjust the amount of light reaching the specimen

Question 16

Which of the following best describes the appearance of squamous epithelial cells from the oral mucosa under the microscope after methylene blue staining?

Accepted Answer

Irregular polygonal cells with distinct cell membranes, granular cytoplasm, and centrally placed nuclei

Question 17

Why is methylene blue commonly used to stain cheek cells for microscopic observation?

Accepted Answer

It stains the nucleus and cytoplasm, increasing contrast and making cell structures easier to see

Question 18

A student observes a slide under the microscope and sees a single circle of light through both ocular lenses. What is this area called?

Accepted Answer

Field of view

Question 19

Which of the following is a correct safety practice when handling microscope objectives?

Accepted Answer

Ask your instructor if you need to clean the objectives

Question 20

If a microscope is described as 'parfocal,' what does this mean for the user?

Accepted Answer

Once an object is in focus with one objective, it remains nearly in focus when switching to another objective

Microscopy and Cell Morphology: Laboratory Foundations in Cell Biology

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