BIOD 171 Exam 3 Questions with 100% Correct Answers

Micrometer (um) Correct Answer - one-millionth of a meter and is commonly designated at 10 ^-6 meters. - used to measure the size of cells Nanometer (nm) Correct Answer 10^-9 meters or one-billionth of a meter - measures cellular organelles and viruses What are the two critical factors that influence your ability to see an object? Correct Answer - resolution and contrast Resolution Correct Answer the distance between two objects at which the objects still can be seen as separate Poor or low resolution means Correct Answer two (or more) objects may appear as one contrast Correct Answer the difference in light absorbance between 2 objects - low light = low contrast Poor contrast gives Correct Answer a high background and makes the visualization of multiple objects difficult How is the total magnification of an object calculated? Correct Answer calculated by multiplying the power of the objective with a 10x eyepiece would make an object appear (40 x 10) 400 times larger (400x) What is one limitation of fixing your sample? Correct Answer -requires you to irreversibly kill your sample. Thus, determining the motility (cell movement) of a sample is impossible. - runs the risk of distorting the specimen shape and arrangement. Phase-contrast microscopy provided what benefits to imaging? Correct Answer - can provide detailed images of live cells without staining. - use of specialized condensers and objectives - amplifies the slight differences between cells and the surrounding background to make the cells highly distinguishable What is the distinguishing feature of dark field microscopy? Correct Answer The light is reflected off the specimen at an angle resulting in a dark background with a vibrant specimen.