This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Techniques – Light Microscope”.
1. Which of the following component of the light microscope illuminates the specimen by gathering diffuse rays from the light microscope?
a) light source
b) eyepiece
c) condenser lens
d) screws
View Answer
Explanation: The substage condenser lens gathers the diffuse rays from light source and illuminates the specimen by formation of a small cone of bright light. With the help of condenser lens very small parts of the specimen can be seen after magnification.
2. Which of the following magnification of the ocular will occupy maximum retinal surface?
a) 1X
b) 5X
c) 20X
d) 50X
View Answer
Explanation: The more the magnification of the ocular, the more retinal surface it covers. However, beyond a certain magnification, the image is not clear (termed empty magnification) even if it occupies a greater retinal surface.
3. Ocular lens forms a virtual image.
a) True
b) False
View Answer
Explanation: The image formed by the objective lens is used by the ocular lens as a second lens system. The ocular lens forms an enlarged and virtual image. The third lens system located in the front part of the eyes uses this virtual image to form a real image on the retina.
4. The resolution attained by a microscope is limited by _____________________
a) diffraction
b) refraction
c) reflection
d) retraction
View Answer
Explanation: The resolution attained by a microscope is limited by diffraction. Due to diffraction, the light emanating from a sample can only be seen as a disk rather than a point of image.
5. 527 nanometers is the wavelength of ______________ light.
a) red
b) white
c) green
d) blue
View Answer
Explanation: The wavelength of 500 to 565 falls in the green color range. 527 nm is used in transmission electron microscopy to improve resolution.
6. The numerical aperture is constant for each lens.
a) True
b) False
View Answer
Explanation: The numerical aperture is the measure of light gathering capacity of a lens. It is constant for each lens and is represented by the following equation – n*Sin*α. The refractive index of medium present is denoted by ‘n’.
7. The maximum possible numerical aperture of 1.5 is for a ______________ lens.
a) oil immersion
b) air interface
c) water interface
d) binocular
View Answer
Explanation: For a lens to be used in oil immersion, the maximum possible numerical aperture is 1.5. The maximum useful magnification of a microscope is 500 to 1000 times that of the numerical aperture of the objective lens being used.
8. The Feulgen stain is used for staining ____________________
a) plasma membrane
b) chromosomes
c) phospholipids
d) mitochondria
View Answer
Explanation: The Feulgen stain was discovered by Robert Feulgen and is used to stain chromosomal material or DNA. For staining using the Feulgen stain, a prior hydrolysis of the tissue in acid is required.
9. Which of the following is used for the preparation of a section specimen?
a) phenol
b) isoamyl alcohol
c) fixative
d) lubricative
View Answer
Explanation: There are two types of samples that can be used in the light microscopy – whole mount and sections. A section can be a thin slice of an organelle that is not viable but retains the morphology of the living structure.
10. A fixative _______________ the macromolecular components of a cell.
a) degrades
b) immobilizes
c) penetrates
d) granulates
View Answer
Explanation: A fixative is used for the preparation of a section – a thin slice of the original organelle retaining all the organelles. A fixative is used for the preparation of the sections; by penetrating the cell membranes fixatives immobilize the macromolecular components.
11. Which of the following can not be used as a fixative?
a) formaldehyde
b) acetic acid
c) alcohol
d) vitamin B12
View Answer
Explanation: Fixatives maintain the morphology of internal structures of sections. Solutions of formaldehyde, acetic acid and alcohol can be used as fixatives. Vitamin B12 however is a nutrient solution.
12. Slides containing adherent paraffin sections are immersed in __________________
a) toluene
b) isoamyl alcohol
c) isopropanol
d) acetic acid
View Answer
Explanation: After fixation the tissue is dehydrated (using alcohols) and embedded in paraffin wax for mechanical support during sectioning. Slides containing adherent paraffin wax are immersed in the toluene which dissolves the wax.
13. Unstained specimens can be visualized using ________________
a) bright-field microscope
b) phase-contrast microscope
c) mass spectroscopy
d) spectrophotometer
View Answer
Explanation: Living cells are small unstained samples that impose difficulty in visualization using bright-field microscope. The highly transparent samples can be seen using the phase-contrast microscope.
14. Which of the following gives a three dimensional quality of the image?
a) Differential interference contrast
b) Bright-field microscope
c) Gas chromatography
d) Spectrophotometry
View Answer
Explanation: The differential interference contrast (DIC) also termed as Nomarski interference delivers a three-dimensional quality of the image. The phase-contrast microscope is another type of interference microscope.
15. Rhodamine is a ___________________
a) fluorochrome
b) antibody
c) stain
d) gel type
View Answer
Explanation: Fluorochromes or fluorophores absorb the invisible, ultraviolet radiation and release a portion of the energy in long, visible wavelengths. Rhodamine and fluorescein are examples of fluorochromes.
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