Understanding Micrometers, Nanometers, and Microscopy Basics

M3: Module 3 Review Due No due date Points 5 Questions 16 Time Limit None Attempt History Attempt Time Score LATEST Attempt 1 75 minutes 5outof 5 Score for this quiz: 9 out of 5 Submitted Oct 22 at 10:16am This attempt took 75 minutes. Question 1 0/0 pts Define the measurements micrometer and nanometer. Your Answer: A micrometer (um) is defined as being one-millionth of a meter and is commonly designated at 10-6 meters. A nanometer (nm) equals 10-9 m or one-billionth of a meter. A micrometer (um) is defined as being one-millionth of a meter and is commonly designated at 10 meters. A nanometer (nm) equals 10~° m or one-billionth of a meter. Question 2 0/0 pts What are the two critical factors that influence your ability to see an object?

Your Answer: Resolution and CTo increase the amount of light going into the microscope you must adjust the iris diaphragm.ontrast Resolution: refers to the distance between two objects at which the objects still can be seen as separate. Poor or low resolution means two (or more) objects may appear as one. Contrast: The contrast is the difference in light absorbance between two objects. Poor contrast gives a high background and makes the visualization of multiple objects difficult. Resolution and contrast. Resolution refers to the distance between two objects at which the objects still can be seen as separate. Poor or low resolution means two (or more) objects may appear as one. The contrast is the difference in light absorbance between two objects. Poor contrast gives a high background and makes the visualization of multiple objects difficult. For instance, trying to identify 2 dark colored objects at night (low light = low contrast) versus the same 2 objects in the middle of a sunny afternoon (bright light against 2 dark objects = high contrast). Question 3 0/0 pts If you wish to increase the amount of light going into a microscope, what part would you adjust? Your Answer: To increase the amount of light going into the microscope you must adjust the iris diaphragm.

The iris diaphragm controls the amount of light that passes through the sample and into the objective lens. Thus, as you open the iris more light is permitted to pass through to illuminate the sampile. Question 4 0/0 pts As light passes through a microscope, what is the last piece that light passes before reaching your eyes? Your Answer: The ocular lens, or eyepiece, directly into your eye. Once light passes through the sample and the objective lens it is directed through the ocular lens, or eyepiece, directly into your eye. Question 5 0/0 pts How is the total magnification of an object calculated? Your Answer: By multiplying the power of the objective and the power of the eyepiece.

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Total magnification is calculated by multiplying the power of the objective and the power of the eyepiece. For instance, a 40x objective with a 10x eyepiece would make an object appear (40 x 10) 400 times larger (400x). Question 6 0/0 pts What is one limitation of fixing your sample? Your Answer: One limitation of fixing the sample is that it kills and could distort the sample. Fixation requires you to irreversibly kill your sample. Thus, determining the motility (cell movement) of a sample is impossible. Fixation also runs the risk of distorting the specimen shape and arrangement. Question 7 0/0 pts Phase-contrast microscopy provided what benefits to imaging? Your Answer: Phase contrast microscope can provide detailed images of live cells without staining. By using specialized condensers and objectives, a phase contrast microscope amplifies the slight differences between cells and the surrounding medium (background) to make the cells highly distinguishable.

Phase contrast microscope can provide detailed images of live cells without staining. By using specialized condensers and objectives, a phase contrast microscope amplifies the slight differences between cells and the surrounding medium (background) to make the cells highly distinguishable. Question 8 0/0 pts What is the distinguishing feature of dark field microscopy? Your Answer: Dark field microscopy reflects light off of the specimen at an angle Unlike bright field or phase contrast microscopy where light passes directly through the sample, dark field microscopy reflects light off of the specimen at an angle. The resulting image is an exceptionally dark background and a vibrant specimen. Question 9 0/0 pts Unlike brightfield microscope, fluorescence microscopes illuminate samples through what spectrum? Your Answer: Fluorescence microscopes illuminate samples through the UV Spectrum.

The energy of the incoming light is in the form of the ultraviolet (UV) spectrum. Question 10 0/0 pts What is the primary difference between TEM and SEM? Your Answer: During TEM the electron passes through the sample whereas during SEM the electron is reflected off the sample creating a three dimensional model of the specimen. During transmission electron microscopy the electron passes through the sample whereas during scanning electron microscopy the electron is reflected off the sample creating a three dimensional ‘shell’ model of the specimen. Question 11 0/0pts Gram staining is based on what basic principle? Your Answer: Gram staining, developed by Hans Christian Gram in 1884, began with the basic observation that different types of bacteria react differently to various dyes. Some bacteria readily take up a specific dye while others do not.

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Gram staining, developed by Hans Christian Gram in 1884, began with the basic observation that different types of bacteria react differently to various dyes. Some bacteria readily take up a specific dye while others do not. Question 12 0/0 pts What is a key determinant in a bacteria being Gram-positive? Your Answer: The key determinant in a bacteria being gram positive bacteria is that it appears purple. Gram-positive bacteria have a thick peptidoglycan layer. The Gram stain exploits this characteristic by using the dye combinations of Crystal violet and lodine. Crystal violet is retained by the thick peptidoglycan cell wall and forms a stable complex with iodine l (upon its addition) effectively trapping the dyes in the cell. The resulting mixture is a purple coloration of the cell. Question 13 0/0pts What is the purpose of heat fixing a sample? Your Answer: Heat fixing ensures the samples tightly adhere to the glass slide prior to staining (and washing) procedures.

Heat fixing ensures the samples tightly adhere to the glass slide prior to staining (and washing) procedures. Question 14 0/0 pts What is the primary purpose of a wet mount? Your Answer: Wet mounts are most often performed to visualize live cells as well as the motility and behavior of an organism. Wet mounts are most often performed to visualize live cells as well as the motility and behavior of an organism. Question 15 0/0pts The acid-fast stain is most often used to identify what specific microorganism? Your Answer: Acid-fast stains are used to identify bacterial stains showing a high degree of resistance to decolorization. Mycobacterium tuberculosis is the most common use for an acid-fast stain.

Acid-fast stains are used to identify bacterial stains showing a high degree of resistance to decolorization. Mycobacterium tuberculosis is the most common use for an acid-fast stain. Question 16 515 pts As a reminder, the questions in this review quiz are a requirement of the course and the best way to prepare for the module exam. Did you complete all questions in their entirety? Your Answer: Yes Quiz Score: 5 out of 5

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