Unit 1 HW3_ Microscope Lab

10/28/23, 10:10 PM Unit 1 HW3: Microscope Lab https://session.masteringaandp.com/myct/assignmentPrintView?assignmentID=10190515 1/7 Unit 1 HW3: Microscope Lab Due: 11:59pm on Monday, October 30, 2023 You will receive no credit for items you complete after the assignment is due. Grading Policy Pre-lab Video Coaching Activity: Compound Microscope Watch the following Pre-lab Video: Compound Microscope and complete the activity below. Part A - Parts of a Compound Microscope – 1 Recall from the video the parts of a typical compound microscope. Drag the labels to identify the parts of the compound microscope. Not all labels will be used. Hint 1. Coarse and fine adjustment knobs The coarse adjustment knob is larger and makes large adjustments when focusing on a specimen. The fine adjustment knob is smaller and makes more precise movements. The coarse and fine adjustment knobs are located next to each other. Hint 2. Mechanical stage and its controls The mechanical stage holds the slide in position for viewing and has two adjustable knobs that control precise movements of the slide. ANSWER:

10/28/23, 10:10 PM Unit 1 HW3: Microscope Lab https://session.masteringaandp.com/myct/assignmentPrintView?assignmentID=10190515 2/7  Correct As you can see, the compound microscope has many parts! Try to identify all of the parts shown in the video. Part B - Parts of a Compound Microscope – 2 Recall from the video the parts of a typical compound microscope. Drag the labels to identify the parts of the compound microscope. Not all labels will be used. Hint 1. Objective and ocular lenses Both objective and ocular lenses magnify the specimen. Objective lenses are nearest the specimen and can be rotated to increase magnification. Ocular lenses are nearest the eye and have a fixed magnification. Hint 2. The condenser and its controls The condenser is a small non-magnifying lens that concentrates the light on the specimen. The condenser has two ways to vary light delivery: the condenser knob that adjusts the height of the condenser and the iris diaphragm lever to open and close an aperture within the condenser. ANSWER: Help Reset Mechanical stage Condenser Light control Nosepiece Head Coarse adjustment knob Stage Fine adjustment knob Mechanical stage controls Arm

10/28/23, 10:10 PM Unit 1 HW3: Microscope Lab https://session.masteringaandp.com/myct/assignmentPrintView?assignmentID=10190515 4/7 Hint 3. What is the relationship between working distance and magnification? The working distance decreases with higher magnifications because the length of the objectives increases. ANSWER:  Correct In microscopy, specimens have depth as well as length and width; therefore, it is important to determine depth with your microscope. As you increase magnification, the depth of field will decrease. Part E - Proper Focusing Technique Recall from the video the steps for properly focusing on a specimen using a compound microscope. Remember to always use both eyes when looking through binocular lenses! Place the steps for focusing a microscope in the correct order from left to right. Hint 1. Coarse and fine adjustment knobs Recall that when focusing on a specimen, the coarse adjustment knob makes large adjustments and the fine adjustment knob makes small (more precise) adjustments. Which adjustment knob will you use first? Hint 2. What is the step before rotating to the next highest objective? Recall that as you increase magnification, the field diameter decreases. Structures in the center of the field will look larger, while structures around the periphery may no longer be seen. If you want to see a particular structure at higher magnification, what step should you complete? ANSWER:  Correct Always begin focusing with the lowest power objective in position, transitioning to higher power objectives; adjust resolution and contrast as necessary. The objectives from lowest to highest are the following: scanning (4×), low power (10×), high power (40×), and oil immersion (100×). Part F - Improving Contrast of a Specimen Reset Help Depth of field Contrast Resolution is the ability to discriminate between two close objects. Parfocal microscope objectives stay relatively in focus when magnification is changed. Field of view is the area you see through the microscope. Working distance is the space between the bottom of the objective lens and the surface of the slide. Total magnification is the power of the ocular lens multiplied by the power of the objective lens used. Reset Help Click the scanning objective into position above the specimen. Use the coarse adjustment knob to move the stage all the way up. Use the fine adjustment knob until the specimen is in focus. Adjust the iris diaphragm and/or the light control knob to improve contrast. Use the mechanical stage controls to move a given structure to the center of your field of view. Rotate to the next highest objective. Clip the slide onto the stage.

10/28/23, 10:10 PM Unit 1 HW3: Microscope Lab https://session.masteringaandp.com/myct/assignmentPrintView?assignmentID=10190515 5/7 Recall the different techniques for improving contrast of a specimen in the video. When you look under the microscope you see the following image. How could you best improve the contrast of this specimen? Hint 1. What is contrast? Contrast is the difference in intensity between the specimen and the background. ANSWER:  Correct By changing the diameter of the diaphragm, you can adjust contrast of the specimen. Contrast can be improved by adjusting the microscope’s illumination in two ways— adjusting the iris diaphragm or the light control knob. Pre-lab Video Coaching Activity: Preparing a Wet Mount Watch the following Pre-lab Video: Preparing a Wet Mount and complete the activities that follow. Part A - Materials to Prepare a Wet Mount Which of the following materials is not used in making a wet mount of cheek epithelial cells? Hint 1. Setting up the lab bench for a wet mount Recall from the video the materials used in making the wet mount of cheek epithelial cells. Rotate the condenser knob. Rotate the fine adjustment knob. Open or close the iris diaphragm. Rotate the nosepiece to a higher objective.

10/28/23, 10:10 PM Unit 1 HW3: Microscope Lab https://session.masteringaandp.com/myct/assignmentPrintView?assignmentID=10190515 7/7 Hint 1. From the beginning Epithelial cells scraped from the inside of the cheek are mixed into physiological saline before they are stained. Hint 2. What is the step before adding the coverslip? Recall that methylene blue stain enhances the visibility of cells by coloring their nuclei blue. If you want to easily see the almost transparent epithelial cells under microscope, what step should you complete? ANSWER:  Correct Always immediately dispose of used toothpicks in a sharps container or a biohazard bag. After completing your observations of the wet mount, the slide can be placed in a beaker of disinfectant solution or disposed of in a sharps container, and the coverslip can be disposed of in a sharps container or biohazard bag. Score Summary: Your score on this assignment is 95.2%. You received 95.19 out of a possible total of 100 points. Reset Help The correct ranking cannot be determined. Add a drop of physiological saline to the center of the slide. Scrape the inside of the cheek with a toothpick. Stir the end of the toothpick in the physiological saline. Mix a drop of stain into the specimen preparation with a toothpick. Place a coverslip on top of the specimen. Place the wet mount on the microscope stage for observation. Obtain the materials to make a wet mount: slide, coverslip, flat-tipped toothpicks, methylene blue stain, and physiological saline.